American culture

In standing up for my American culture, I stormed out of a party. As Vietnam would have it, I was trapped in the house because you need a key to get out. When the person who lived in the house finally came to let me out, I told him he offended me and he basically told me to get out of his house and he didn't care how I felt about any of it.

Lesson learned: it's okay for everyone to (excuse my language) shit on America, especially when there's only one person there to defend it (me). BUT as soon as someone starts to shit (excuse me) on Germany ... NOOOOO that's not okay. (Let's just forget the reason WWII even started.) I can take the criticism in stride, I know we're not perfect. BUT as soon as you tell me that Germany is perfect and other countries (namely America) have no culture, you're just wrong. We have EVERY culture, and that's what I think makes us who we are. But, according to this guy, American culture didn't begin until 20 years ago. So, what, I was 6? What did we have before that? I know America has a dirty past and continues to get into trouble, but that doesn't make us uncultured.

Am I wrong? Did I do the wrong thing? Stand up for the wrong beliefs? It's so hard being the only American in my circle of friends sometimes.