I figure that even if the people of the town collected enough money to cover the discrepancy, the discrepancy is still on the record and if it would have led to George’s arrest before the donation, it would still lead to his arrest even after the donation.
I believe the standard answer to this annual question is that we see the bank examiner put in his own donation, so we have to assume that he’s going to overlook any temporary discrepancy. Besides, Clarence’s boss is apparently running this whole show, and he has a lot of clout.