Question

is the united states in the western hemisphere?

Answer 1

Yes, the easiest way to determined if something is in a specific hemisphere is get a standard map and put your finger on the place in question.
If your finger is north of the equator you are in the northern hemisphere.
If it is south it, you are in the southern hemisphere.
If it is east of the Prime Meridian then you are in the eastern hemisphere.
If it is west you are in the western hemisphere.