Even credit cards seem super backwards in the US with them actually taking your credit card and giving it back to you (and your tip being just written down on a slip of paper).

How does that work with things like the porter who takes bags to the hotel room? Or the person who cleans the room?

Maybe they aren’t supposed to be tipped, as we never got the hang of it and blundered about trying to avoid causing offended.

Personally, I just stopped doing that.the tips were small to begin with.

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

In a case like this, you should bring cash with you anyways. It is a different situation than going to a restaurant. When you travel one should always have cash, even if one normally doesn't. It's common sense.