mobilepay is pretty ridiculous for a foreigner to use actually. You are required to have both a danish bank account and danish telephone number in order to use it. For this reason alone, it can never take off entirely. Until there comes a way that one can use their home account in a foreign country (with fees) like a card, then it will never reach the same levels of adoption.

In the US this isn't reliable. I just got a new phone and learned the hard way it doesn't support NFC, and even if it did a lot of merchants disabled their NFC readers waiting for more merchant-friendly rails to reach the market.

Swish is (sadly) popular for p2p payments and "lemonade stand"-size "businesses", but good luck paying with it in a traditional store.

That is a non-cash solution which is insubstantially different from a plastic card.