The United States does not have an official language:

Despite common belief, English is not the official language of the United States at a Federal level. It is the de facto, official language because 82% of people claim it as their mother tongue, and 96% say that they speak it 'well' or 'very well.'

There have been, however, numerous proposals to make English the official language at the Federal level. They're usually attached to immigration bills, but they usually never make it intact all the way through.

This hasn't stopped individual state from making English their official language, however. 28 out of the 50 States have made English their official language in different times.