trouble is blackrabbi it doesnt matter what nationality you are, no matter what you post, if people wish too they can find something which will reinforce their stereotype view of your home country and its people. unfortunatly your argument about helping other countries etc probably isnt the best thing to type.
at the moment usa is unpopular in may parts of the world, it is patently unjust to blame any one individual in community for a country's actions (unless your really george w bush
(joke)).
unfortunatly there are always idiots in every community, be they online or real world. hence you get the agro from idiots online and you heard of attacks on muslims after 9/11 even though they obviously had nothing to do with the attacks, they ,like you, were just the wrong "type" in the wrong place at the wrong time, or rather the right "type" in the right place at the right time for someone to vent their feelings.
these people that gave you problems may actually have a genuine dislike of USA, in which case they shouldn't take it out on you, or more likely they decided it would be fun to wind you up, in which case they succeeded. as mentioned before anything like this happens, save a record of it, contact admins etc, don't rely on just posting here as its just their word against yours.