Puerto Rico isn't a state yet, though, and neither is D.C. (I say D.C. should be part of northern Virginia, myself).
I'd for sure say, let's annex Mexico and make it the most southern state in the Union. That way our Chrysler plant, and the Motorola Integrated Circuit plant, will be truly U.S. endeavors.
Plus, we could relocate Taco Hell's headquarters to somewhere in the State of Mexico, fire all the people that have been in charge of the ingredients and the menu for all these years and replace them with local Mexicans, and get some REAL Mexican food going in the fast-food business!