This series is not aimed at senior or elite skaters only. It's for all skaters who would have been eligible to enter regionals (i.e., a few thousand individuals spread out across the country), but with later dates to allow skaters more time to prepare in case their rinks had been closed for months.
And to accommodate skaters who might now be based in different locations from where their home club is -- including some who used to train at training centers and are now home with their parents.
And to choose skaters to compete at Nationals, at junior as well as senior level.
The locations were chosen to spread out across the country so that singles skaters could find an event within a day's drive of wherever they happen to be, although if they're going to take advantage of the opportunity to do two they'd likely need travel further.
Some of the locations had already been scheduled to host regional (on earlier dates) or sectional competitions. Others were added to fill in geographic gaps. I'm sure much negotiation was needed to find appropriately located rinks that could offer sufficient ice time and safety protocols in the general time period, with host clubs willing to organize.
The ice dance locations are actually convenient for a large number of the junior and senior teams from 2020 Nationals who are based in Michigan, Illinois, or New York, Pennsylvania, and DC area.
In case you're interested in where the senior skaters at last year's Nationals were from:
ladies
pairs
dance
men
You can also look up the junior competitors for more geographic variety:
Event Results for 2020 Toyota U.S. Figure Skating Championships
ijs.usfigureskating.org