That's probably true but we also have like two major supermarket chains, so I think it's hard to make the case that government regulation is the only cause of monopolies.
The USA actually has a history of disallowing large, centralized private banks. So-called unit-banking, driven by a powerful small-bank lobby created a great deal of instability in the 19th and 20th centuries. Canada and Scotland have a history of much freer banking than the USA. This is a very interesting subject, and I highly recommend reading a bit about it.