I understand, you being American. To clarify, "it" referred to the "the word data", not its grammatical number.
By the way, “being” is a gerund, so it’s “your being American”.
At the risk of veering very deeply into the weeds: to my ear, "you being American" sounds acceptable. I think it parses correctly (though differently from "your being American").
It sounds like something Dickens might have written.
Is it grammatically acceptable English? I mean here and now?
It's hard to research this subject. My standard reference, B A Garner
Garner's Modern American Usage, Oxford (2009) refers to it as "Fused Participles", following the discussion in Fowler's
Dictionary of Modern English Usage, Oxford (1965).
He approves of Fowler's belief (if not his absolute dislike) that "Especially in formal prose, the possessive ought to be used whenever it is not unidiomatic or unnatural" (Garner).
Garner has grades for usage evolution, and rates the non-possessive (e.g., "you being American") as Stage 3 ("widespread, but...), which is better than Stage 2 ("widely shunned") and worse than Stage 4 ("ubiquitous, but ...").
I'm not a pedant, but I try to write carefully. Of course, nobody speaks as carefully as he can write.