It wouldn't matter where the N American instruments were, since they get averaged with the ones from China, Australia, wherever, in calculating Kp. I don't know why the USGS monitoring should seem to be unreliable; and 70 miles away shouldn't be a big problem in terms of seeing if they're getting what you're getting, but if the data aren't available that's that.

You don't by any chance have an aunt or college pal or similar in Chicago or Dallas or somewhere, whom you could persuade to set up a duplicate of your instrument? My suspicion is that they would get just as many signals as you do, despite the absence of local earthquakes.