People dont hate the usa as a nation, it is a beautiful country and there are every many great things about it. Obviously their government infuriates people with their meddling in other countries affairs whether it be counterproductive or not. They are not some peacekeeping government and will go down along with the islamic groups as the most destructive force of this generation. The reason why as you say 'people hate americans' though is simply through their actions and words. I don't speak of nearly all americans and knew a lovely guy from Miami and also there are many great americans on here alone but there are way, way too many a number who speak total and utter nonsense and are just very ignorant of other nations and people.
If these americans kept these views to themselves people wouldn't be so unkeen on them but they dont. I am british and I have heard so many americans say 'you'd be speaking german' or 'we saved you in ww2' that i've lost count. The US government and schools teach a biased and frankly incorrect world view to americans who then argue until they are blue in the face and make infactual statements as they don't know any better. The UK fought off Germany alone in the battle of britain in that war and made gains in africa while russia were already making great gains against the germans before the usa even entered. There was no saviour mission. Also more commonwealth troops invaded Calais than American and russia suffered countless more losses. To hear amerians then make these ignorant comments is reason alone for many to dislike the usa.