Down and dirty truth. Most of those countries talking bad about US citizen tourists have a rather large US military presence as well. We are briefed to keep a low profile, and most of us do. There are some, however, who refuse to be a gracious guest...like one poor chap who was in Panama when I was there. He refused to follow the advice of the people who know, and found himself near a large anti-US demonstration. Unfortunately for him, he was wearing a t-shirt with old glory on it, and the phrase "Try and burn this flag". Luckily, the police were in the area, and all he got was second degree burns on his chest and back...
Some people never learn. As I've stated before, I'm sure there are people like that in every country...thing is, most of them never travel outside their own state. Trust me on this. I've been to places where the people treat me quite well...until they find out I'm an American. Those places were Victoria, BC...Gander, Newfoundland, and a small club in Germany...but the German club doorman didn't want me around because of my race...
...at least he was honest. The manager of the club, OTOH, was quite upset with the doorman when he saw me turn around to leave. I didn't catch a lot of what the manager said, but quite a bit of it was language you don't generally use in public.