... The OFAC list is all foreign entities...
I suppose that depends on your definition of 'foreign'. The OFAC lists contain a number of US entities; individuals, companies and charitable organizations.
Also,..., others have done an excellent job of explaining the compliance principles behind a 'risk-based' approach to sanctions checking.
I will add an operational/tactical perspective. It could be more trouble than it is worth to add exceptions to your systems and procedures.