So non-US actors will have access to what banking data and source code?

What’s the problem with that? If non-US actors wanted to wreak havoc in the country there are much lower hanging fruits (that would also provide better “returns” on investment) than infiltrating a banking startup.

But few as thoroughly regulated. Wait until the regulators fall off of influence from those capitalizing on the outsourcing take. See PPP as an example of the system turning to new ventures to actually get anything done and the zenith of offshoring in general.

Do you really think your US banks have no overseas operations / outsourcing centers?

These will be increasingly attacked politically as the extent of identity and fraud on cloud become more common knowledge.