How has your local area changed due to immigration?

I don’t doubt that poverty and education etc. have the ultimate influence, but I don’t realistically see how it is possible for culture not to be a major part of the issue.
If you live in a place where (e.g.) littering is culturally normalised and almost everyone is doing it (including you), and then you move to another country along with thousands of other people from the same place, and all settle down together in one area with hardly any exposure to the local culture, why would you suddenly stop littering? Likewise if you migrated in the same way from a place where littering is culturally frowned upon and almost nobody does it (including you), why would you suddenly start littering?
When Japanese football fans go to watch the World Cup in other countries, after their team plays you can always see hundreds of those fans going around the stadium cleaning up their litter (and indeed other people’s litter). Most other countries’ fans don’t do anything of the sort; they leave their litter there for the stadium staff to clean. What possible reason could there be for this, other than the cultural norms that exist in their respective home countries? Is it a coincidence that Japanese cities also happen to be some of the cleanest in the world?

The problem is again confounding. You're not comparing countries or communities that are like-for-like in all regards except this problem, so you cannot say that culture has a major influence on it. There's also the sampling issue, e.g. are the Japenese football fans that travel abroad representative of all Japense football fans, let alone all Japanese people?

I don’t really understand what you mean.
We know that there are strong Japanese cultural norms against littering (e.g. in a Japanese cinema, customers are expected to take their popcorn containers away and dispose of them personally, unlike in a European one where it will be part of someone’s job description to clean that stuff up at the end). We also know that Japanese cities are some of the cleanest in the world, so people living there are on the whole less used to dropping or seeing litter. (They also don’t tend to provide public bins; people are expected to take their litter home).
Given this information, how can it all be irrelevant when it comes to the behaviour of Japanese football fans? What other reasons / confounding factors could there possibly be for why we almost always see Japanese fans cleaning up the stadium en masse but almost never see European fans doing it, which are completely disassociated from their place of origin?

The issue is that you cannot conclude that culture plays a factor, let alone a significant one, because there is no way to quantify it.

You aren't comparing cities / countries that are exactly the same in all regards except for (say) littering, so you cannot conclude that culture is a reason why the amount of littering differs between them. You don't have a control group, basically.

Why do they need to be exactly the same in all other regards?
If my point is that the societal background you come from affects how likely you are to litter, then why wouldn’t it be enough to show that littering exists much more prevalently and is much more normalised in one society’s population than another?
Sure there could be deeper reasons why one society litters more than another (poverty, education etc.) but what difference does that make to my point? It wouldn’t change the fact that people from one society litter more than people from another.

Because if they aren't the same in all other regards then you cannot assign the difference to any particular factor (in this case cultural differences).

You cannot look at two completely different economies, point out the differences in their amount of litter and say 'this is clearly because of cultural differences'. The logic doesn't flow, there could be a dozen other reasons why the amount of littering is different.

This matters because if the reasons people litter are not cultural at all then it undermines your claim that immigration has "ruined" your city.

But we’re not talking about the reasons why littering is different in one society compared to another. We’re just pointing out that it is different in one society than another.
When I say “cultural differences” I just mean the fact that some behaviours and values are more normalised in one society than another, regardless of what the deeper reasons might be.

Right, but it matters if you want to argue that littering done at the hands of immigrants is because of a cultural difference (and that it more severe than would-be littering at the hands of British people).

What do you mean by “cultural difference”? It sounds like you’re using this term differently from how I am.
The way I’m using it: if something is more normalised amongst one group of people than another, that is a “cultural difference” in and of itself (even if some other reason behind it like poverty or lack of education exists).

Sure, but my point still stands. It goes back to one of my original questions: if the immigrants in your city were instead British people then, all else being equal, would you see the same amount of litter?
This relates to your original point, that immigration has ruined your city because they do not follow British / European culture (hence there is a cultural difference between groups of people).

If by “British”, you mean ethnically, then no I don’t think it would make any difference, if all else were equal.
But if you mean “born and raised in Britain, amongst a representative sample of other British people” then I think you would see less litter. Because by growing up in this sort of environment, each person is more likely to have been taught from a young age and in stronger terms that littering is wrong; they’re less likely to have grown up seeing almost everybody else littering; they’re less likely to be accustomed and desensitised to seeing large amounts of litter on the street etc. compared to those who are born and raised in the hometowns of these particular immigrant communities.

How do you know that? You're making several assumptions which may not be true, namely that A) the differences in littering between communities / countries is due to a difference in sensitivity towards it, B) that migration between said communities would also carry over that sensitivity (or lack thereof), C) that the immigrants in your city originate from a community where there is this desensitivity and D) that British people, if they lived in these areas themselves, would have greater sensitivity towards littering.

All of these are essentially the consequence of one single principle, namely: More litter being dropped in an area is (at least in part) caused by, and evidence of it’s inhabitants having a greater general inclination to litter (or equivalently, a lower sensitivity against litter).
I don’t really see how that “may not be true”. In order for a place to get littered, people need to be inclined to drop litter (and vice-versa).

Again, how do you know that? You aren't just claiming that these people are willing to litter, you are claiming that they have significantly higher willingness to litter (enough to "ruin" your city) and that they wouldn't have this willingness if they followed British culture.

If by 'following British culture' you simply mean that they are littering in any capacity then the issue isn't cultural, it is the root reason(s) why people litter at all (e.g. poverty).

I know that because in my experience, the towns and cities where their communities originate from have significantly more litter than anywhere in Britain. And also because, post-immigration, the areas that they inhabit within Birmingham have started to have significantly more litter than anywhere else in Birmingham.
There is also a large park in my city which sometimes hosts generic events (e.g. the Olympic Torch lighting ceremony, music concerts etc.) and sometimes hosts events more directly targeted towards immigrant communities (e.g. the Big John’s Mela, Eid prayers) and invariably they are far more littered after the latter type of event. A similar thing happens at the local cricket stadium - again, far more littered after a South Asian nation has been playing, in the specific areas where that team’s fans have been sitting. (I know that because I’ve worked as a volunteer for both places, and one of my duties was to pick up litter).
All of which indicates a significantly higher inclination to litter in these specific communities of people compared to the general population of Birmingham / Britain.
No I don’t mean that; by “following British culture” I mean not being a distinct, isolated community that has its own, significantly different level of inclination towards various behaviours (like littering) compared to the general population of Britain.

Do you know every one of these immigrants in your city and their country / town of origin? If you do, how do you know that their littering in the UK reflect their desensitivity and nothing else (e.g. relatively higher poverty and lower education than the non-immigrant population)? Are the places elsewhere in Birmingham, where littering doesn't exist to the same extent, identical to these communities in all regards other than where the inhabitants are from?

It remains your assumption that these communiteis do have a significantly different level of incliation towards these behaviours, specifically one that wouldn't exist if the people living there were British instead.

I’m not saying that their littering is the result of desensitivity “and nothing else”. I’m saying that it’s a result of the communities’ overall inclination to litter - evidenced by the fact that those communities litter to such a significant extent (relative to the general British population).
I fully agree that there are probably several underlying factors behind that higher inclination to litter (like more poverty, less education and other things too). But I don’t see why that changes anything I’ve said. They may explain why the inclination to litter exists in those communities but they don’t negate it.

It changes what you've said because you have blamed the immigrants for not following British culture, when the problems that exist could easily be caused by non-cultural factors (e g. poverty, lower education, etc).

I don’t consider those to be “non-cultural factors”. The culture of a community is shaped by a lot of things, including poverty, education and any other feature of the environment it develops in.
As I said, by “cultural differences”, I simply mean that some behaviours or values are more normalised in one society than another. I’m not referring to the causes of those differences.