Fwiw you can tip with credit cards everywhere now. I don't think tip receivers like it, but tipping sucks, they can deal with it. I don't carry cash anymore.
Maybe they aren’t supposed to be tipped, as we never got the hang of it and blundered about trying to avoid causing offended.
I think people also know non Americans aren't going to get it right. If they're the type of person to get offended over that, I wouldn't spend my time worrying about their opinion of me