It is not unlikely that this is the allegory they had in mind primarily, but so much of the bigotry and hatred depicted applied to gays, blacks, jews, women and probably more groups, too.

We're rhyming history, every generation we're trying to overcome prejudice, oppression and hatred against a new minority, only for some to conjure up a new distinguishing feature to define a minroty to be ostracized. It feels like treading water sometimes, can't we just cut through the bullshit in one go, but no, we have to go through all the steps, while some new group (or a subgroup of a previous group) has to endure all the pain this brings. Sometimes it feels like we're not really getting better. But maybe we are. But it's still too slow, it still repeats itself, and nowadays we might experience multiple such cycles in our lifetime, when at some point it took generations to get that kind of progress?

Ah, I'd missed that detail. I was on the fence about whether or not it was a trans allegory because it didn't initially feel like there were as many similarities in her story to being trans as there was to homosexuality and being an undocumented immigrant but upon further consideration I have to agree. Though it does seem to me like it is also about those other groups I mentioned. I suppose it's a bit of a catch-all (which worked great).

There were also parts of it that could easily be interpreted as Jim Crow era politics. Passing was a thing for Blacks as well. Splitting into two different cities reminded me of both redlining and "separate but equal." Of course, history repeats itself, and this allegory could also be applied to Jews, Native Americans, and any other persecuted minority, including gay and trans people. Una's whole situation could pretty easily be mapped onto a "don't ask, don't tell" situation as well.