Well, in this case, it's only an emotional reaction towards US's support of Israel in the extremely sensitive situation going on right now with Palestine.
I'm not saying it's right to say it, just that it's understandable, giving the circunstances.
Also, don't forget that the US is the most powerful and richest country in the World. There are bound to be some jaleous people, and there are lots, but that too is normal. Just inside the US, how many people hate Bill Gates?