In Europe contactless payment is nearly everywhere - nearly every store supports it. Even in Germany (which is historically very pro-cash), since Covid more and more people pay with card and many of whom pay contactless.

In the EU we have some rules that even contactless payments with card sometimes, but not always, need to have some kind of additional authentication in the form of entering your PIN. Contactless payment methods via phone or watch don't have this need because they already have their own authentication methods. That's why so many people pay with their phone or watch. Its just more convenient and always contactless. (no PIN needed)

How is it in the US? Are things like Apple Pay still limited to certain stores?

In Europe? Debit cards. Hardly anyone uses a credit card in a supermarket.

If I'm going out I'll have both a debit card and cash in my wallet. Given that large scale outages of payment networks are no longer theoretical but to be expected, not carrying cash is just silly. Since I have a wallet in any case, I see no point in using contactless payments on a smartphone — I usually don't take it with me when getting groceries.

I have no idea if I can even do contactless phone payments on GrapheneOS, but since everything else works (including my bank's app), I don't care.

I think it's healthy for a population to not have as part of day-to-day life to pay with credit, effectively paying with money you might not actually have, going into debt. How many US citizens are crippled by credit card debt, and the interest on it?