The US uses the metric system. SI units are provided by Federal Government for almost every quantifiable product produced by a federal agency and its been like that for decades. Often they use a mix of customary and SI units, providing conversions between the two in official reports. Generally you see customary units communicated when work more directly impacts the general public with more technical work using the SI system. Many industrial fields use predominantly the metric system as is the case for medicine and many engineering fields.

The US does not use, exclusively, the metric system because many units had been adopted by convention prior to the formalization of the modern international SI system and for cultural or historic reasons people don't want to change.

That's not so different from other places where measurement systems in common use are often retained.

The metric system debate is, for me, one of the most interesting cultural bugbears on the internet. Because it does not really matter that much what system of measurement a nation uses, its really not going to impact your life that much at the end of the day. Particularly in the modern era where conversion is as trivial as looking up a calculator online. But for whatever reason people get huffy about the metric system.