I get where that question comes from, but I think it's the wrong question. The real question is, how would any realistic action that would cause US companies an

I get where that question comes from, but I think it's the wrong question. The real question is, how would any realistic action that would cause US companies and people to spend more of their money in the US affect global trade in the aggregate? While all participants in global trade are net beneficiaries, the US has done particularly well. Protectionism is usually a two-way affair; if we make it harder for us to spend money abroad, other countries will likely reciprocate. This doesn't somehow even out to make us (or them) better-off for doing it -- it simply contracts the global division of labor and introduces deadweight loss, decreasing the overall efficiency of the system and making all parties worse-off... except for a few well-connected companies that get artificially protected from competition and have enough connections to lobby successfully for price supports or other pork benefits.