Also, unless your plan is to exclusively export to the US, then it's less cost effective to open up new facilities in the US. You just raise prices and and have the consumers take the hit for the tariff. There's also the problem of logistics for raw materials for whatever products your manufacturing. Those also tend to cost more to acquire stateside.

The worst part is that policy is only a single bullet in the policy foot gun Trump has loaded. It gets even more expensive when the low cost labor is suddenly deported and/or put in camps. Which I realize isn't even the worst thing about the immigration policy, but just pointing out that it too has consequences to these same people.