Well, ALL countries use the metric system, including the USA!
The USA helped standardize the metric system and adopted it in Thomas Jefferson's time. SO the metric system is more "American" that the Imperial System!!! ALL US Customary measurements are based on metric definitions.
And ALL scientific fields only use metric even in the US. Even Tesla only uses metric! And so do you! Seconds, amps, watts, tire sizes are in metric. You use it more than you think!
But to give you a literal answer, ANYONE that speaks English in the world uses the English site. This includes the USA, Austalia, Great Briton, Belize (formerly British Honduras), and English speakers everywhere in the world. About 360 million people to 1.5 billion speak English as first/second language respectfully.