Earlier quoted context omitted.
Being a well-off 19yo engineer in Poland I can't even imagine being treated unequally in everyday life, so that's yet another reason to not visit US for me, other than almost certainly being questioned at a border (although 90% of my income comes from startups in California).
If you're a stereotypically ethnic Polish person (just guessing from the username) no one is going to even look cross-eyed at you if you can speak English at all. The 21 year drinking age is still idiotic and actively harmful.
The United States (from my perception) seems to have far more establishments serving alcohol, whose policy is to ask identification for everyone (or if not everyone, a ridiculously over-heavy subsection of their clients, eg "we check ID for anyone under 35"). Probably for CYA reasons.
I don't ever recall any place in Europe asking for ID when buying a beer over in there (even when I visited when I was in my mid 20s). Whereas, I still occasionally get asked for ID in the United States in spite of being over 40.