This is the case for every country. You just see it with the US a lot more since it of course has the biggest footprint on the English-language side of the internet.
Pushy, ignorant, reactionary, racist, isolationist, nationalist. Stick our noses into the matters of other countries where we don't belong. Assume everything is centered around us. War/military happy. Arrogant. Loud.
Not sure if I'm missing any, but these are the prevailing things I see when people are talking about the US and the people who live here.
What is hard is that there are of course people (many people, even) that match one or multiple of those descriptions. But the same as it is silly to generalize all of Europe (or even any one European country), it is silly to generalize all Americans.
According to one source, the only media that for a long time made it into the states is media that the US government approves of. I could go into detail about it, but it shows up quite prominently in this video.
I think other countries are a lot more open to self deprecation as part of their humour / culture. Not saying there aren't some examples of this in America, it just doesn't seem to be as prevalent as in British comedy for example.