The problem is that Ford isn't really that much of an American company anymore. Well they kinda are, but money has no borders today. Beyond the possible PR gains which evidently weren't enough to convince them, they couldn't possibly care less if the jobs they create are in small-town America or in India or China or wherever. The important part for them is how much returns they can get on their investment. And obviously they get more returns by having labor that's magnitudes cheaper and less demanding on the benefits front.
If tariffs are imposed, they will just slap the costs on consumers, just like it's always been done.