[yariang]

There's many small banks like you say, but the impression I get (I have not done the research to back this up) is that the few really major banks (i.e. Bank of America) have a huge market share. Again, I have not researched this, but just from day-to-day experience, it sure seems that way.

Edit: http://www.cardhub.com/edu/bank-market-share-by-deposits/ According to this site, the market share of the top 10 banks is about 45%. Those statistics are not highly precise but it illustrates the point I am trying to make.