In simple terms, there are a lot of commercial banks in the US although the number is declining due to mergers and acquisitions. Structure is due to regulatory history, particularly old limitations on branching and inter state banking.
Structure is very different in other countries.
US model of a large number of competing privately owned banks is unusual. Follow the process from bank to bank to see how much multiple deposit creation occurs. The FOMC met today. Demand deposits D Loans Time deposits, etc. Avoid monetizing the debt Prevent govt.