But they (we) do use debit cards as one tho.

Mastercard/Visa are not only credit cards - they're used for debit card transactions as well.

Americans use credit cards as the default payment method? Why?

Credit cards have by far the best in-person UX of the options that I am presented, tap my card or phone and leave and they're accepted everywhere in practice (my debit card is not).

The 'cardholder can always reverse any charge' behavior is also nice once every few years.

Fraud protections are, by law, much stronger in favor of consumers for credit card transactions in the US.

If you have good credit, you can also get 2-4% in credit card cash back on everything via rewards programs.

Fraud protection, mostly.

If someone steals your debit card and spends all your money, you might very well be fucked.

But (in America) if someone steals your credit card and spends a bunch of money, they technically stole money from the bank, so it's the bank that might be fucked, not you. All you have to say is "yeah that wasn't me" and the bank reverses the transaction.

If you're blatantly abusing this the bank will end their relationship with you and cancel your card, but that's pretty much worst case scenario, and you won't be on the hook for anything. And they obviously make enough money off of people who carry a balance and pay interest that they still come out way ahead.

I use it because if I used a debit card and it gets compromised then I lose whatever's in my bank account. Maybe I can get it back if I can prove it's fraud?

If I use a credit card and it gets compromised then my cash is still secure. If I have to fight a credit card company for 6 months to get the payments reversed I still have cash to live off of. If I don't win then hell I don't pay. Maybe I go to collections and credit gets dinged but my real assets are still mine.

To boost credit rating. When you have none credits, your credit rating is ZERO, and it is considered bad. So you could pay for example 10$ (yes, small amount) from zero percent credit, and regularly pay it and this will effectively raise credit rating.