Where does the voltage in a circuit go from 120v down to 0v?
Think of voltage as electrical pressure.

It doesn't "go" anywhere. It is the difference in potential between point A and point B. You can never measure voltage at a single point, it is always in comparison to another point. So, if you put both leads of your meter on the same electrical point, as you did with the neutral and the ground since they are terminated on the same electrical point, you read zero. Birds sitting on a high voltage wire are only touching the wire at one point and there is no comparison point for a measurable voltage. So they are not hurt.

We create electricity by creating a difference in potential (voltage) between two points and then allowing the difference to flow (current) through a load (resistance) to create work.

As long as you don't get between those two points, you are safe.

Learn more here for free. Go to the education tab for the open source textbook and lectures.

Good luck in you learning and stay safe!