Factories get built in the U.S. all the time. Since there is some amount of competition for them between states, the typical approach is to shop around for a nice deal, where the state/city will usually not only offer to shepherd you through the environmental/approval process, but actually pay for it or subsidize your construction, and give you 10-20 years of tax breaks. Happens with car factories all the time. Even Apple is doing it with the A5 chip manufacturing facility it announced it's going to open in Austin.