I understand that the USA was originally a British colony so it seems it should be obvious that English would become the dominant language.
It is, however, my understanding that there were MANY languages spoken throughout the nation. German in the North, French in the South, and wasn't Florida a Spanish colony?
So what was it that gave English the edge in a nation where contracts were routinely drawn up and business frequently done in multiple languages? Especially given that there was not (and remains no) "official" language in the United States?
Florida was not originally part of the United States. Neither was Louisiana. When they did become part of the US they were rapidly flooded with English speaking immigrants who outnumbered the speakers of Spanish or French.
There were never large areas where German was the majority language, so German speaking immigrants usually learned English (or the second generation did) (Not always. The 'Pennsylvania Dutch' (or some of them) still speak a German dialect as a native tongue).
Native American languages, of course, were common. Few are still spoken in the original 13 states (though more in other places in the US).
Dutch was originally spoken in New York and New Jersey (when they were both part of New Netherlands), but after the English captured them, English speaking immigrants soon outnumbered the Dutch speakers. This was well before the Revolution.
Swedish was spoken in parts of Delaware, when it was a Swedish colony, but even before it was taken by the Dutch (and then the English) there had probably become more English speakers than Swedish speakers there.
The main immigrants in the early history of what became the 13 original states were overwhelmingly English speaking. Their increasing numbers of descendants were English speaking. Those who spoke other languages found that their kids soon learned to speak English.