For background, I've lived in southern England for seven years. I have loads of friends here. No one has ever been rude about the USA to my face. If anything, they're too pro-America, in the "Why would you ever leave that wondrous place to come to this rainy dump" sort of way. When I explain my reasons for moving, they say, "Well, OK, I guess, but I'd love to live in America!" Why would my experience be so radically different to Lalala's? How can two people living in the same place see things so differently? Logically, it has to do with differences in those two people, not in their surroundings.
Here's the thing: If one person reacts negatively to interaction with you, then it's likely due to some problem that person is having, but if everyone you interact with has the same negative reaction, then the balance of probability suggests that there's something in your behaviour that they are reacting to. That was the point of my Justified a**hole quote. Even if you're not intentionally doing anything, people can sense if you have extreme negative feelings about something, and they will react to that.
This is the only point I'm trying to make. But if you think it's more logical and more constructive to condemn an entire nation and everyone who lives there based on one very subjective criterion without giving any thought to other possible interpretations of the facts, well, that's on you and so are the consequences. I'll save my sympathy for people who need it.