Very interesting that the USA are in this case less integrated than the EU.

Paypal prefers 48 different state licenses as Money Transmitter over buying/starting a US bank or credit union. (In Europe they started as an EU-wide licensed E-Money Issuer (based in UK) and now are operating a bank in Luxembourg.)
https://www.paypal-media.com/licenses

I like the idea of a Bitcoin user powered credit union that provides a regulatory framework for Bitcoin-to-fiat-money transactions but agree with Stephen Gornick that buying a bank is easier (much faster, maybe cheaper as well) than starting your own bank or CU.

Maybe this article about Paypal's regulatory situation in 2002 might be helpful:
http://www.zdnet.com/news/fdic-decides-paypals-no-bank/121346

As MTs need licenses in each state it is possible to register on a state-by-state basis after a regulator complains there. For Paypal, it was the easier way to grow slowly that way.