Offering economic incentives by making it easy to generate revenue from direct sales seems unlikely to stem the flood.

If you don't like the competition then you should be happy they're limited to ad revenue in the App store, which will only be the right solution for a subset of apps.

If you've got a moral issue with American companies being slow to enable other options for developers in certain nations then you need to think of a better way of expressing that than worrying about them "flooding the market" with their products and implying that they're substandard.