What are some rude things in Japanese culture that some Westerners might do without thinking? And maybe vice versa?

-it's considered very rude to blow your nose in public in Japan, whereas in America it's okay.
-public drunkenness is very acceptable in Japan, but in America you can get arrested for it.
-the rules about shoes inside is very strict in Japan, but in America nobody pays attention to it. The only rule is to wear shoes when out in public.
-it's good to make slurping noises when eating noodles in Japan, but in America it seems rude and annoying to eat loudly.

What else? :)

A random observation

When meeting new people in Japan, I've noticed that sometimes one of the first things they notice about me is my piercings. I have 7 in each ear, 00 gauge plugs in the first holes, my eyebrow, and a labret piercing. I am always met with a look of curiosity at first, then fear. They ask me "itakunai?" "doesn't it hurt?" I'm not sure if they're honestly curious if I am in a constant state of pain with my piercings or if they mean "did it hurt when you got it done?" like Americans will ask. I'm not really offended by it, but I've answered the question so many times I don't really have to think about it anymore. I guess I'm just a little bit taken aback by their audacity and straight-forwardness in asking me about them.

I've been thinking lately about language barriers. I've been finding it a fun challenge but also a little bit frustrating getting around in Japan. I've had a couple of experiences where shop employees help me out the best they can with the English they know, and for that I am exceedingly grateful. They are catering to my needs, even though I am a guest in this country. Other times, cashiers will ask me or tell me something in Japanese that I hardly understand, and I'm stuck there looking embarrassed and stupid because I don't know what they said. I'm not sure whether to be flattered that they expect me to understand, or to be frustrated with them because I am obviously a foreigner. It's my responsibility to learn the language, and of course I don't expect them to speak English to me. I'm not sure what to do in these sorts of situations while I'm learning Japanese in the meantime. I don't want to make foreigners look bad either. I guess I'm just feeling kind of stupid right now.