Agreed. To get to anything other than English, you need some significant changes along the way. A few options:
1) You could potentially have much broader (and deeper) Spanish colonization early on. In the most extreme case, this could have the main colonies be Spanish and a revolution against Spain. However, if that were the case, it's unlikely that the Constitution would resemble OTL.
a) In a lesser case, you could just have more Spanish colonization such that (as the English take over) a much larger percentage of the people have Spanish as a main language. Then, around the time of the founding Spanish is pretty common and becomes more so as more former Spanish colonies are included. This might get Spanish recognized as a second official language.
2) Likewise you could have more successful French colonization so that French was far more common at founding. Then, perhaps with some loving zeal at French support, you could have French be a second official language.
Likely it wouldn't be the US in that case, as the US is the current version of a state founded out of English/British colonies, by a largely English speaking elite/majority. Even the decolonised new states of the 20th century have largely kept English as an official language of government and commerce, to some capacity, as it is rather hard to expunge a language with such a wide presence.