Curious of there is a maximum amount of cash or food that a country can hold on hand?

No limits. You lose .1% of your food each turn to decay as well as .1% of any cash over 2b.

Assuming they are using 64-bit ints in PHP, the max is about ± 9,223,372,036,854,775,807, so basically what Tmac said :D

I didn't realize you couldn't go past quintillions! My bad, lol.

good to know