You have a voltage of 110v – 120v on the average outlet. When you plug in a six outlet power strip why, or how, can you still get 120v out of each of the outlets in six outlet strip? Why does it not become 20v in each outlet?
I guess the same applies to the entire house. You have 120v coming in and yet 120v is available at each outlet regardless of how many outlets and how many thing you plug into all the outlets.