As a non-US citizen/resident, I can't wait for Americans to finally riot against tipping, just so they stop doing it abroad. A shame that it had to take comical proportions domestically for people to start questioning it. Americans tipping abroad while on holidays ruins service for everyone that isn't American – as a non-American you are guaranteed to get worse service than a American in touristy places (and sometime…
I’ve never tipped 20% in places without a tipping culture, but I must admit your comment makes me think I should — at least, in the places where a tip would not be considered insulting. I tip in the US to receive better service. If it’s not considered rude to tip, and it results in better service, why wouldn’t I do that?
This of course doesn't apply if you are a regular, feel free to do whatever you want. The staff will treat you well because it's you, not because of the stereotype your accent implies.