In the US, owning a bank changes the regulatory status of the entire legal entity structure. This cannot be evaded with shell companies, etc. Specifically, “any company that controls a bank” is a Bank Holding Company and is regulated by the Federal Reserve (regardless of where the controlled bank is chartered). Being regulated by the Fed is a big deal and they can and will poke around in your non-bank subsidiaries (which are, after all, assets of the Bank holding company).
What if there's one parent company whose subsidiaries include amazon and a bank? Since "amazon" itself isn't controlling the bank, it's not subject to said regulations.
