I think you’re making it harder than it needs to be. Trump isn’t promising special favors for an individual company. He’s telling individual companies tax rates will come down for everybody. Might as well stay. You are correct, lower taxes are not the reason an American company moves production to Mexico, it’s cheap labor. If you tell them they can save money on taxes, and the cost of moving they will probably stay in the USA. That’s all Trump is doing.
What about the $7M in tax incentives that Carrier, and no other Indiana business, got?