Belgian banks made a study about the impact in various scenarios and guess that the damage in worst case will be about 10% of the Belgian export to the US, that is about 500million €. Belgium mainly export chemicals (including a lot of pharma) and food/drinks (read: chocolate and beer) to the US in direct export and technical parts (like loudspeaker drivers) to other countries to use in products exported to the US (so indirect export). The US mainly import digital services (software, subscription services, banking) and natural gas and oil to us, but those last ones is only minor. They think the impact will be there, but minimal.
But where i think the US will be the one with big problems, is that they don't have the production facilities nor the knowledge anymore to produce higher quality technical products. Those factories where moved to other countries because it was cheaper decades ago. You can't recreate that fast. Europe did that far less, and still got a lot of production plants around. We relied a lot less on import to get our stuff. We still got companies that make electronics, or even the everyday household items and clothes. They are often not the cheapest, but not that expensive neighter.
If the international trade shuts down, and each continent needs to rely on their own stuff, Europe will have some serious hicups, but will remain strong. The biggest impact will be on natural resources, but even there we got way more than most expect. It was just not exploited anymore since WOII because we could get it cheaper elsewhere. Our mines were shut down because they were to expensive, not because they were empty.
I'm not so sure if the US economy can survive that. Not because of the lack of natural resources, but because the skills and infrastructure to mass produce is largely gone. And as the average US citizen is a big spender, their stock will run dry very fast, faster than they can recreate the production facilities and skills.
But the protest against the policy is growning, also very strong in the US i hear from various sources. I don't think this policy will remain long as even in the US most see what damage this will do on the long term, especially to the US economy. And that worries everybody, even many who voted for this gouverment. Because they probally see in everyday bussiness that nobody still trust the US and tries to avoid dealing with them. I know that a big (multianional) client from me (i'm an IT consultant) was considering expantion to the US, but the scrapped that scenario and will remain in the EU because of the actual policies. They don't export or import to the US, they work now in Europe (mainly) and Asia and will keep doing that.