You seem to be confusing state law with federal law, and how preemption applies.

Banks are governed first and foremost by state law. State banking laws are very easy to adhere to. State/local banks do not have to be FDIC insured.

HOWEVER, once the state tries to offer services over state lines (to out-of-state customers, or out-of-state locations), then federal laws kick in. (Federal laws automatically kick in if a bank reaches a certain size.) Federal laws also apply to transactions between banks, where either bank is subject to federal laws (or if one bank is in a different state from another).

Finally, you vastly overestimate the lobbying prowess of national banks. Local/state banks have significantly more influence with politicians b/c they are in-state institutions (i.e., profits get taxed by that state; their executives are local businessmen instead of New Yorkers).