Can’t they just reject it on the grounds that America uses English as the de facto language? In Texas they might also allow a Spanish sign but that wouldn’t provoke the same xenophobia.
So if I needed to interact with the USA government (appear in court or apply for a driving licence) I'm entitled to do this in the Welsh language?
I ask this facetiously, as both English and Welsh have official recognition in Blighty.
Based on the civil rights act, it is considered discrimination based on nationality to discriminate based on English proficiency, and therefore illegal.