[kerowo]

If someone is going to leave their country and start a life in the United States I don't think it is out of line to ask them to adopt the customs of the United States. Likewise if an American moves to another country I would expect them to adopt the customs of their new home.

How to do it isn't as easy, but bending over backwards to be tolerant of someone else's old customs without encouraging them to adopt new ones is probably not the best way to do it.