I'm in North America. Today, people answer "Thank you" with "No problem."

That's a common response in Australia too. Another one is "too easy".
Oh, OK, I'll make it harder for you next time.

The response to "thank you" I most often came across in US was "sure". I don't know what the correct reply to that should be. Umm, "yes I'm sure I want to say thank you?"