The Musk supporters feel that universal automation is coming fast and I bet the Chinese being as industrious as they are will seize upon that to make up for their demographic issues. They are already he world leaders at renewables and nuclear and regardless, their ability to ramp up carbon based fuel sources is second to none.
Meanwhile the US appears to have an okay demographic pyramid(especially compared to their peers) but birth rates are declining and all the ingredients to increasing birthrate are not in the upswing (good incomes, cheap real estate, stable governance). Now you are killing off the US's golden goose (immigration) it seems like you are repeating the mistakes of China.
Hillary famously said "those jobs aren't coming back". I do not know if she was incorrect in that, but I suspect she might have been right. I don't see a viable path to that happening, and I've yet to hear anyone else describe such.
Training for what? What if our population of working age people is far larger than our economy's ability to absorb whatever sort of service worker you imagine they should be training to become? Given a fixed total population, there's only room for x masseuses or y graphic artists. If we have n unemployed people needing training, and that number is higher than x and y combined (for any sort of x and y), telling them to retrain doesn't solve their problem. Some are going to lose out. The truth of the matter is that by offshoring manufacturing, we created an economy where there is a surplus of ultimately unemployable people.
A message of training isn't just bullshit, it's transparent bullshit. Most people have an intuition that this is the case, after all. As for midterms, both the Republican and Democratic parties have a different strategy. They will simply import voters who will vote for them. H1Bs for the GOP, and the remainder of the naturalization pipeline for the Ds. It's slow, but they're willing to put in the longterm effort.