The founding fathers didn't really see the need to establish an official language as English was already the de facto language of the nation. I believe they have thought about making English the official language various times throughout history, although it's a somewhat controversial topic. Many areas of what makes up the modern United States spoke other languages apart from English (Spanish, French, German, indigenous languages, etc.), and today there are of course many communities in the United States where other languages are dominant.

Why would we? Your question goes right to the heart of what is a country. Is it a rational organization organized and directed from the top down? Or is it a collection of people, behaving as human beings, forming relationships and organizations spontaneously on their own, and organizing itself as a nation from the bottom up? The United States was conceived according to the second model.

Keep in mind that in the early years England was an enemy of America. Also America had non-English-speaking colonists and received aid from non-English-speaking countries. English was just the de facto language- it wasn’t a source of pride.