You do realize, you are drawing a parallel between them and us (the West) that even during our period of Industrialization did not exist. The future is not always a mirror of the past, especially with difficult cultures and political regimes/empires. There are many, many reasons that conditions may not improve. In fact, there are likely more arguments of why it will not when they try to be even more competitive with us after Jan 20. Your prediction is short sighted.
And what happens on Jan 20, nothing really.
Trump has no magic wand, factories and infrastructure and supply chains all take time to build.
Or, to put it another way, by the time mid term elections are held, no new jobs will have been created in the US, lots more may have been lost in companies who export (US$2 Trillion) as tariffs on US exports by other countries made ones from China , the EU, etc more cost competitive, e.g. Airbus, Samsung,Panasonic, Toyota,etc etc etc etc.
This could see punishment in the polls.
End of term, few if any major players (Apple, HP, etc etc etc) will have started manufacturing by that stage.
Trump is gone, policies are reversed and the world carries on.
Its not just the factories, where is the power, the water, the raw materials, freight haulage, etc etc comping from, all of that takes years and years to happen. Where do 300,000 workers come from ? Where do they live, what about schools, hospitals, roads, water, sewerage, electricity, police, fire, internet, phone, shops, car mechanics, we are talking of a city of over 1 million people by the time you add in all the other services a population needs.
How soon can a city of 1 million people get created ?
But what happens if they go down the automation route, few employees. Well other US manufacturers will jump on that band wagon too, a rush a new automation will cause a fall in costs making it cost effective for a lot more companies. This will lead to few jobs comping back to the US, and a lot of jobs lost to automation.
AI is going to have a major impact, its going to change almost everything and will replace a LOT of jobs.
Instead of trying to bring back non existent jobs back to the USA, the US would have been better to start panning on what to do with a very large number of unemployed. The world has possibly hit (or soon will) peak employment, AI and automation is only going to see employment ratios head one way....down.