Will a "universal voltage" component work in US?

Usually this means there is a switch on the product that lets you chooses between 115v and 220v. Regardless, it will sound a bit better at the voltage used in its design (so if it is from the U.K. or elsewhere in Europe , at 220 v).

If you think about the true meaning of "universal" it should work on any alien spacecraft or any planet.

This is only the ''Known Universe""

Except tuners. Technically they will work, you just won't hear much.

When I said "universe" I meant it in the "universal" sense that encompasses everything that exists or does not exist, known or unknown, knowable or unknowable. And a truely universal piece of stereo equipment will (DOES) work anywhere!