First, Yes, in survey and study after survey and study, popular opinions do tend to be starkly different in what you can consider former Iron Curtain Countries vs "Western" Europe; and these differences extend to Race and Sexual Orientation in a negative aspect. To this you can add in a healthy shift to Nationalism and backlash towards immigrants (Though this affects more than just the former Soviet Bloc).
However, the extent that it would affect you depends a bit on your expectations, your age, and actions when there. The advice below is basic, and probably applies to an extent if you were Black, Asian, Hispanic, and to an extent Gay. As a Mexican American, you will likely see less of a reaction.
In general, I agree with many others, you will be seen as a tourist and an American, and treated as such, seeing little to no issues.
An exception might be if you are very young, then you may get more unwanted attention from shopkeepers, restaurants, etc. who may doubt you are a "tourist" and likely a "poor student" or simply not there to spend money. The other might be if you are looking to interact with the locals "romantically", as one extreme example above points out, it can be a bit touchy, and of course, putting yourself in situations late at night or involving alcohol always has the potential to go bad.
Do expect though that you will be treated as a tourist, a guest, so if you are looking to "live like a local", be taken in and treated as family, that probably won't happen. Larger cities should be no problem, and you will go about with hardly a second glance, in very small towns and non-tourist areas though, you may notice a bit more attention, more curiosity than aggression.
Overall, go, enjoy yourself, have fun.