In general we don't really dislike the Americans any more than we "dislike" the French
the Americans I've come across in person have all been very nice (if somewhat loud and eccentric) people. However, I find a lot to dislike in American society so I do slag off the country, as opposed to the people, if that makes sense.
I don't like the politics of the US because it's so right wing compared to Europe. I don't like hearing about the evils of contraception, the teaching of creationism in science classes, the right to own a gun (and carry out horrific mass shootings...), the evils of having any kind of welfare state, socialism being used as a serious insult, the massive pro-Israeli bias, the rejection of climate change, the idea that America knows what's best for the rest of the world, and most of all the idea of American exceptionalism and getting all arrogantly emotional at political rallies thinking your country is superior despite all the flaws I've listed.
I also don't like some of the social phenomena that are held to have arrived from America, like obesity, individualism/commercialism, everybody sueing each other, racial segregation. It also bugs me when Americans show how little they know of the outside world and its languages, cultures, and just where things are on a map.
Some of what I've said will be clouded by stereotype but a lot is informed by reading about and generally observing American politics and society. As I said, the people themselves as individuals have always seemed really nice