I put my vote in for Americans being the most hated.
Many of the people I know from outside the US feel the general American is a pompous and arrogant SOB, the government is somewhat warmongering and in general Americans would screw pretty much anyone if they saw a profit in it. Oh yeah, and Americans are stupid.
Let me add this is a very broad generalization.
Racial profiling can be justified, if at all, only if it is likely to be effective, but there is at best a very poor correlation between “looking like an Arab” and “being a terrorist”. The second-greatest terrorist outrage in American history was perpetrated by an American of anglo-saxon descent. Even in regard to the present crisis, we know that not all al-Qaeda operatives are, or look like, Arabs, and there has been at least one attempt to blow up a plane involving an Englishman of West Indian descent.
By all means engage in profiling to identify figures who present a greater risk of being terrorists, but this must mean profiling by reference to relevant criteria - movement patterns, travel habits, known associates. Sure, profiling by reference to ethnic identity is a great deal easier, but that doesn’t mean it’s any use.