Depending on how much money you throw at it and how much support you get by the government in dealing with regulatory processes, moving existing complex plants could take 2-5 years. Add another 1-2 years if you start from scratch. However when starting from scratch you have to do the same in other places too, so the relative time loss gets smaller.

Fact is some megacorporations already announced that they want to invest into manufacturing in the US because of tariffs. It will not offset the broader impact but help Trump sell his tariffs as a success.