I think you missed a few points in your theoretical calculation. Let's look at an actual pumped storage reservoir, one conveniently linked from the Wikipedia page you linked to. https://en.wikipedia.org/wiki/...

The upper reservoir has a capacity of 27 billion gallons, and peak output requires 33 million gallons per minute, so it can run for 13 hours with 1872 MW output. (To be more than fair, I'm ignoring the fact that you can't REALLY drain the lake completely dry each day, and that power is reduced as the level goes down. Actual power capacity may be half of what I'm charitably calculating). Giving pumped storage the benefit of the doubt, we'll say Ludington could do 1872 MW X 13 hours = 23,765 MWh.

That's 8 * 10^10 BTU

So we need 120 * 10^15 BTU and we've got 8 * 10^10 BTU. Hmm, 15 facilities the size of Ludington would be 120 * 10^10.

But we need 10^15, not 10^10, so we need 1,500,000 facilities the size of Ludington.

The upper reservoir of Ludington is 2.5 square miles. 2.5 miles X 1,500,000 facilities = 3,750,000 square miles. The continental US is 3,119,884 square miles. So, looking at actual performance of actual pumped storage, covering the entire US with pumped storage reservoirs still wouldn't be enough - even for the UPPER reservoir. Typically, the lower reservoir is quite a bit larger than the upper.