Trump can't do a thing about this!
He can't and he won't be able to offer subsidies to miners, which will really go bad with these other voters, he has little power on state level and more than that it's impossible for a country even the size of the US to offer better electricity tax deals than everyone else, including corrupt governments elsewhere!
That being said, the US will definitely hold the majority of the hashrate for years to come, with China out of the game there is simply no large enough player on the market with that much cheap energy available, like space capacity to compete with the US. So while Trump's promise is just another promise, a 66% percent will most likely happen naturally.