The United States currently has no official language. Give that the predominant laguage spoken in the U.S. is English, and considering that all of our historical and government documents are written in English, including (but not limited to) the Declaration of Independence, the Federalist Papers, and the Constitution.
The majority of nations have an official language, even if other languages are spoken by a significant part of the population. English is the de facto but not the de jure official language at the federal level. Congress conducts its business in English, our laws are written in English, and our courts use English. Our Founding Fathers mainly came from English speaking nations. Thus, English should be declared as the official language of the United States.