Swede here, I worked at an American/Global company's internal IT helpdesk for 4,5 years, and I can't say that I have ever met an american I have actually disliked, at worst I felt ambivalent, but for the most part I just felt generally positive towards them.

Worst users I have worked with based on nationallity tend to be people from UK, it was not unusual for them to act slightly superior to us lowly IT servants, don't get me wrong, most Brits I have met are great guys, but when working with some of them, they seem to be stuck in a strict classist society and be very much aware of that we were below them, which does not work in Sweden.