There are plenty of US traders that haven't been honouring their trades either. I always emphasise that there are sharks and unfair people in every part of the world and you shouldn't generalise.
That being said... Yes, Europeans are frowned upon. And that really saddens me sometimes but it can't be changed. The only thing you can do is just not think about it and do what you do. After a while, people will realise you're to be trusted and you'll start to meet US traders that regularly buy/trade with you and they'll talk about it to their friends, etc... And after a while you'll realise that the people who choose to generalise and not give you a chance aren't worth your time of frustration. Everyone makes their own choices and if someone chooses to refuse your offer(s) because you're European, so be it. Leave it at that and leave.
This is a lesson I learned myself, I've been stuck in a corner a lot because people judge me for being European. But I don't let it get to me, there are more people that accept me than people who don't and I'm happy with where I (and most of my European friends) am now. I've met some amazing international traders.