John Saw at Sprint, with an extremely limited budget, covered 11% of the US population in April 2019. Simply by upgrading existing cells, he's covered about 20% of New York, (At the top of the map is where I live.)
He hasn't yet reached most cities in the US or the most populous areas of NY, the black areas on the bottom of the illustration. I believe when he upgrades more cells, Sprint will cover more than half the US population.
In mid-band with Massive MIMO, Sprint's 2.5 GHz has reach comparable to the traditional lower bands. Sprint's 1800 MHz covers 95%+ of the city. The 5G coverage will be similar when the other cells in NY are upgraded.
Sprint's 160 MHz of spectrum at 2.5 GHz is one of the best holdings on earth. Saw already is getting good and sometimes contiguous coverage without adding any new cells.