Two points. First, the US does not have an official language. Second, the original 13 colonies were settled by the English, who spoke, well, English. Those colonies together formed the United States of America and sought and achieved independence from England. While there were undoubtedly French and Spanish speaking citizens of the young nation, the overwhelming majority spoke English and descended from English culture. All early official government documents were written in English. Since this time, although there have been millions of non-English speaking immigrants, English was the first language used in the country, and English remained the dominant language. But, again, English is not the official language.