Power steering pump?
 

About a month ago I had my power steering pressure hose replaced because it was leaking. As I understand, this is a pretty common repair for a Maxima with 150,000 miles.

As soon as it was fixed at the dealership, we moved across country - the car gave me no issues to entire way.

Fast forward to today, and while I was driving on the interstate I just lost power steering. I don't hear the pump kick on at all, and the reservoir is filled with fluid.

Could the pump have gone out as well? Just poor timing?

Dumb question. The belt is still intact yes?

The pump doesn't "kick on" or off. It is always pumping when the engine runs.

Start with the basics and check the belt that runs the pump like Donkeypunch said. And check the tension of the belt, don't look to see if it is there.