Does Nationality of someone have a big impact on relationships? Watch
Although saying that some foreign accents are perceived to be better sounding, so certain accents may actually get you less chance of being turned down. Also different ethnicities look different (obviously) so that will have an effect but whether that's good or bad will depend on the person so I guess it's a bit irrelevant.
But people won't normally reject somebody purely on the basis of "They're not from where I'm from", unless they're really rather racist and obnoxious and frankly, stupid.
However I am an Oriental guy who is culturally British and but still struggle because white girls are not attracted to Oriental guys.
They are 'primary barriers' because they restrict how people come to know each other; you are more likely to approach and get to know someone who has similar interests and lifestyle to you. What is the phrase...'birds of a feather flock together'? This is terrible example but take a Pakistani individual who enjoys playing cricket and goes to a club (trying not to be racist), then take an Oriental individual who does not particularly like cricket, as is the way of things in East Asia. They are less likely to meet and create some form of relationship in the first place.
Now this effect will be reduced if both individuals have had their 'original' culture diluted by living in another country. If this 'primary barrier' is overcome, the two individuals from differing cultures can form a platonic relationship, especially if they share some interests.
If we are talking of 'romantic' relationships then the two factors come into play again. It may be difficult for people to try and live together with someone of a significantly different culture or religion. It can be harder (but I'm not saying impossible) for, let's say, an atheist to live with a Muslim. Lifestyle is drastically affected which may cause people to feel that the relationship is too difficult to maintain.