If MacArthur had immediately begun construction of fortifications on Bataan and shifted food supplies there (there a was a half million tons of rice available in warehouses near Manila) then they could have held out for a lot longer than they did. The Japanese never had an overwhelming force and unless they committed a lot more troops, then the defenders might have held out for a year or more. As for getting relief convoys through, that was unlikely.
The longer Bataan held out, the more political pressure the US government would be under to "do something". Bataan could become to the US what Przemyśl was to the Austro-Hungarian empire or Verdun to the French.