It wouldn't matter if they were requiring citizenship. The protected category is national origin. Companies can't normally require native-born citizenship but any company can refuse to hire non-citizens.
Citizenship is a pretty common requirement in information security in sensitive industries, to use the example I'm familiar with.
>>0xBDB+(OP)
Yeah, that makes sense. Who would deny a naturalized American all the rights and privileges? I don't know what people are getting upset about; I don't see anything that says "requires a native-born US citizen."
It says "US ONLY US Citizen," but that only excludes people who still swear allegiance to King Charles.