Declare any nation that deals with or harbors terrorists an outlaw nation and withdraw all recognition from them. Fine ANY US company that does ANY kind of business with them or with any country that does business with them.
Make the banks account for WHERE large deposits come from. If they can't, they must refuse them. If the bank refuses to cooperate, close them down and transfer their assets to other banks that are compliant.
Draconian?
You betcha!
Politically explosive?
Absolutely.
We may be left standing all lone?
Possibly.
But we wouldn't be putting American lives on the line in an interminable war.
Think about it.

troll