I mean… No other nation put “America” in their name. And “United” and “States” are even more generic. Heck, “United States” isn’t even distinctive.

• “Uni” is already “university”,
• “Statist” is already something else
• Statian / station
• Stater / stator
• Unitian / munition
• “Unitarian” is already something
• Unit 👎
• Unish 👎
• Ustan / Houston
• UnStan, UnStian, UniStan, UniStAm👎
• “Yank(ee)” is almost exclusively derogatory, and a fair chunk of the nation uses it to denigrate a different chunk.
• “Yu-ess-ian” is just unbelievably aweful
• Usonian didn’t take off, but we could give it another go.