It's an interesting question. Keeping in mind the levels of "foreign" aid we maintain now, I would suspect... yes? Is there a transition that American politics makes from the state level to the federal level, that makes us more generous? Is there a reason for that transition, or is it simply magical?

In the case of California specifically, the difference between federal taxes paid and federal money received represents about 7% of the state budget. Foreign aid is about 1% of the federal budget, though. Why would California spend more? (Edit: Of course its budget might have to triple if it didn't get all that federal money, so there you go.)

Foreign aid is just a tool in the soft diplomacy spectrum. It's not usually given out of generosity, but to influence local politics, develop markets etc...

Is there any reason to believe that those factors would not apply?

One good reason of a stable relationship (as in states of a single country) is not needing to spend time and energy with diplomacy, freeing those resources for use abroad.

If the military-industrial complex could be coopted into building schools, roads, railroads and hospitals instead of weapons, soft diplomacy could change the face of the planet.

For a fraction of current prices.