To build a T.A.R.D.I.S. would help the united states as well as many other countries. The reason it would help us would be because the government needs to know how to time travel that way, as other time travel devices are made the people of the world know how to use them wisely, other wise we will end up with paradoxes. This will also help us in space exploration and it will answer questions such as how the universe was really made, how the dinosaurs really died, etc. etc. It will help us study other planets, and if they are a threat to the universe, such as the asylum of the Daleks, and scaro the original planet of the Daleks. If the planet is a threat we will blast them with the death star.
We should start building a T.A.R.D.I.S. by the beginning of 2014.