I agree wholeheartedly. My assumption was that such behavior was simply a symptom of the relatively larger proportion of Europeans on this site, and their obvious jealousy and insecurity regarding Americans. I still believe that is the most likely explanation. To be clear, America has done hella dumb shit lately, and is deserving of criticism on many fronts. But what OP is referring to goes beyond that. It's emotional animosity that overflows the bounds of reasonable criticism and targets individuals rather than governmental decisions or policies.
The number of times that I have seen people refer to the American contribution to WWII as cowardice, meaningless, etc, is too damn high. 400,000 Americans died in that war. Read a fucking history book you ignorant, insensitive fucks.
It's certainly possible that there are agents in our midst sowing divisiveness, although unlikely. I don't have any beef with any nationality, because I don't judge people based on where they were born. That should be common sense, but it's apparently difficult for some people to wrap their heads around.