There are major theoretical problems with extending economic logic to nation states:

• Nation states are not market actors. They rely on coercion, so we can't use the logic of mutually beneficial voluntary exchange to infer anything about welfare increases.
• Even if we could describe a nation state as having a welfare function, we know from social choice theory that there's no coherent aggregation of individual preferences that generate it. That means there's no reason to expect a relationship between the state maximizing its utility and real people increasing theirs.
• Public Choice Theory offers the most coherent treatment of "state actors" and that description is of a small set of individuals increasing their utility at the expense of everyone else.

Many parts of the service sector are vastly more scalable than manufacturing, because they offer services globally without any need for massive amounts of global transportation infrastructure.

You are right that labor reallocation requires economic opportunities for that labor. It's possible I'm being naive, but I think we could have had sufficient labor reallocation if our economy weren't made artificially rigid through unfathomable amounts of regulations.

My expectation wrt foreign subsidies is that it should impoverish the subsidized population and benefit us, because they're basically just stealing from their population and giving it to us in the form of discounted goods.

To me the more interesting question here is the ethical one. Using tariffs to even that out is similar to boycotting slave products. By charging those producers the difference, they no longer benefit from the subsidies and may as well stop (assuming our tariffs would go away in that event)

I also think tariffs need to be given more thought by our camp. They've been bizarrely much more maligned than other taxes and I'm definitely not convinced they're the worst form of taxation.

If increasing tariffs can be used as political justification for cutting income/payroll/inheritance/capital gains taxes, then we might be much better off.