It depends on what Trumps ultimate goals are.
We assume it's about doing best for America and it's people. Except that's not how Trump has ever operated. It's always been about what's best for Trump.
He has a shed load of debt. That's affected by interest rates. By driving the interest rates down he's writing off his debt and he still will have purchasing power. Indeed he will have moved because he will be less laden with debt. The value of things within America will go down because he can off shore in other currencies and because lots of people further down the chain will go pop.
This works for obligarchs. It enables them to get richer and the rest of the population to get poorer. It's an enslaving mechanism to remove power from the American people. It's how disaster capitalism works. It also will allow America businesses to move in and buy up everything in places like Lesotho. Or effectively all but take them over. Their currencies will be devalued too, thus meaning that the cost of goods to Americans may not go up as much as people think. Because it's those at the bottom of the chain who pay the price most. It will be in the form of starvation. Where this falls down is in how it's likely to drive more wars too. But hey who are the worlds weapons manufacturers?
We are seeing China trying to do similar to this to an extent with it's belt and road initiative - extend influence with loans and the insistence of using Chinese companies as conditions for the loan for infrastructure. This move is going to make it much more difficult for China to continue to do this - because it will be trying to prop up its own economy instead. Instead it gives the US the opportunity to move away from an aid model to an ownership model where the US has control of overseas assets and to extend influence in a way more similar to the belt and road approach. This is where talking about Greenland also makes a lot of sense.
Trump is an ultra capitalist. He thinks of everything in terms of owning it. That's how he sees American futures. It's a different type of American Colonialism and exploitation of non Americans. One that doesn't value the lives of people living elsewhere. The bonus is that in decimating African economies he'll drive African migration to Europe which will destabilise Europe politically in his favour too.
He could literally back down on everything tomorrow with this now and he, personally will still win, because trust in America has gone and the stability and safety of the American market has gone due to his recklessness.
Yes it might wreck the US economy in some ways. But it also gives enormous opportunities in others for the super rich.
If you see all of this through the lens of how it benefits the super rich it makes sense. Trump has no interest in the lives and experiences of normal people. He has no capacity to comprehend them as he's so removed from that experience.
Far from being a losing situation for the US, it has the potential to work the other way for obligarchs. Its closer to the model that Putin used when he took over Russia. It led to a huge rise in criminality in Russia and a decline in living standards but Putin is still there. It is easy to see how the US could go the same way and how Trump could aspire to that. Putin, despite this, retains a huge popular following because he trades on nationalism and traditionalism. This again works for Trump in the context of the US and the Christian Right and ideas of nationalism particularly in red states.
It's really messed up.
Trumps trade mark is to do one thing, double down reverse and the deny he ever did to the contrary. He holds two opposing positions at the same time in this way - allowing his supporters to always take the line they line and deny the other. And it gives little room for the opposition to have any traction because the truth and the power to observe and recognise the truth is undermined and destroyed. This there can be no accountability.
So I don't assume that Trump will follow through. He doesn't necessarily need to. He just needs to break the existing system and exploit the cracks that emerge. And to hell with those who fall through those cracks. Trump regards them as losers - he refers to them as losers. They are worthless to him. Why should he care? Humans are just another resource to be exploited.