Sweden/Iceland is the target/paradise, cards only.
Also for crime stop... everything is trackable.
Maybe after this COVID world war the new system will accellerate in that direction, no more touchy touchy papers/coins.
Sweden; I have cash, but I never use it.
Denmark: Same.
UK: Same.
France: Same.
USA (Las Vegas, including road trip from LAX): Same. Did not even bother with exchanging any money. I still have a 1$ banknote in my wallet from the last time before I went there.
Germany: It's like the 1970s, you better know where your closest Kreissparkasse is, because you'll need to visit their ATM.
Italy: Mixed bag. Venezia was easy. Firenze was so-and-so -- ice cream parlor did not accept cards
-- but their sister coffee shop did, so I had to run between them and haggle a bit. Naples was batshit crazy. No-one accepted cards. Especially not the two guys in leather jackets at the
"long-term car park" who were standing around smoking and in a strange way very reassuringly were able to convey the feeling that as long as I paid them, cash, the car would spend three days on their dusty lot, and the only thing that would happen to it was that a cat had walked over it. The paw-marks were obvious.
I am not very proud of the fact that I've most likely fed cash into the extralegal economy of the Italian south, but it is an experience I at the same time don't want to be without.