I think pretty much the only time I've ever felt awkward here was a few weeks ago, when there was full-page editorial in the Scottish paper basically making fun of Americans. This guy was actually there on holiday when he wrote it, and he actually had the balls to go on and on about how grotesquely fat Americans are, how rude the kids are, how it's impossible to embarass us, and making all sorts of wisecracks. To top it off, he said he loved everything about America, except the fact there are Americans in it.
I know it was meant to be tongue-in-cheek and I probably should have just laughed, but it annoyed me that he was rubbing in stereotypes and many people here may not know otherwise. BUT, I think for the most part Americans are very much accepted here, so I didn't let that bother me too much.
Also, like others on here have said, I don't think the American superiority complex is limited just to Americans. I see it here in Britain every day!
I think pretty much every country thinks it's better than others, at least in some ways. It's "national pride", I guess?