The United States does not have an official designated language.
Historically, many languages have been used and over 500 languages are spoken by the U.S. population, the most common, of course, being English (specifically, American English), which is considered the de facto national language.
As you may have guessed, Spanish is the second most spoken language in the country. There are also many indigenous languages, some of them endangered.
A bill known as H.R.997—the English Language Unity Act—was introduced in 2017 in an attempt to make English the official language.