This article from Marche 2016 covers some of the issues:
UK’s Lessons For US Mobile Payments Adoption
"OK, you say, so all we need to do now is hustle up and get contactless POS terminals out there in massive force.
If it were only that easy.
In the U.S., there simply aren’t the same dynamics in play.
Two million contactless terminals today sounds like a great start — until you do the math. There are something like 13 million POS terminals across a massive geography that is the United States, not including mPOS devices.
The U.S. is also a market in which there are 1.2 billion payments cards in circulation, more than 47 billion debit card transactions, more than 26 billion credit card transactions and 209 million adults over the age of 18.
Oh, and something like 14k financial institutions that issue those cards and countless merchant acquirers and ISOs all hawking merchants to deploy new terminals.
It’s a whole lot harder to wrangle this ecosystem to the ground given the diversity of merchants and the engrained plastic card habits honed by consumers over the last 50 or so years."