What’s stopping a new competitor to come in apart from regulations? You would expect someone already trying that given how profitable it is
The contracts with merchants prohibited them from accepting other forms of payment.
https://www.justice.gov/archives/opa/pr/justice-department-s...
Yea, I think you have this one backward? it's lack of regulation that allows Mastercard and Visa to say "if you do try to use some other payment process you can't use us". Since MC and Visa own all of it, no business can take that hit to their customer base
Some other countries don't have this issue for various reasons.