The United States does not use the Imperial measurement system. The Imperial Measurement systems was codified nearly half a century after the United States broke away (codified in 1824 for anyone curious). We use the United States Customary Units which while similar to imperial is in fact different in a variety of ways.
Also great litmus test; say any neutral on either imperial or us customary units. All the most annoying people will respond to hate on it even though you weren’t praising, or even wanting to debate it.