I can't speak for other countries, but I'm not too surprised that you can run into certain cultures of Americans who seemingly have zero regards for the sentiment of others. Maybe it is ego and entitlement, but it's not because they can't be deported.
I don't think the risk of being sent back (or lack thereof) is important for how to treat other people. To put it crudely, assholes will be assholes no matter where they come from.