In reply to "Thank you!":

Americans prefer "You are welcome."
The British prefers "Not at all.", "Don't mention it."

Instead of saying the above, can we say "No problem.","Thank you.",
or just give a smile back without saying anything?

I read a travel story written by a Chinese talking about his tour in Australia. He was impressed that each time he thanked an Aussie for
any help or kindness, he got a "Thank you" back. He was very much amused by this, "Who should thank whom?"

:) Thanks!