The U.S. has more banks than anywhere on Earth. That shapes the economy in many ways

The Bank of Bird-in-Hand in Pennsylvania is one of the country's more than 4,000 lenders. It has thrived by catering to the Amish community in the town of Bird-in-Hand. Its mobile branches, like the one pictured here, travel to remote parts of the state, carrying with them ATMs and a teller window. (Bank of Bird-in-Hand)

Silicon Valley Bank, Signature Bank, and now, First Republic Bank.

The failure of three smaller lenders in less than two months has shaken the entire global banking sector — with potentially major economic ramifications. And the banking turmoil continues, with shares of regional lenders such as PacWest sliding this week.