In New Mexico between the western New Mexico border and Pie Town (hwy 60), I have seen strange looking gray skies that are in areas designated as being Bortle 1 skies. At dark sky sites in Arizona the skies are gray, but the ones in NM are a different kind of gray. The grayness seems to be more solid, if that is possible. Although the NM skies are classified as Bortle 1 skies, they do not seem to have an increased number of stars that are visible to the naked eye. One astronomy associate related seeing a once in a lifetime sky at the Grand Canyon where there were so many stars that it was difficult to pick things out. These NM Bortle 1 skies are not anywhere like that. What is the explanation for this disparity of stars? One explanation is the grayness is sky glow but from what I read sky glow has a bluish color, not a gray color, and the sky glow is normally within 15 degrees above the horizon, not the entire sky. Are these NM Bortle 1 skies really that good, or are other atmospheric effects destroying the astronomical benefit of a Bortle 1 sky?
Stan
Without actually seeing just what you are seeing it is a bit difficult to precisely judge the problem. But, overall I honestly don't take a lot of stock in today's various light pollution maps, at least beyond as a rough approximation. At least one of the maps even suggests that my local conditions are growing steadily better over time when, in fact, they are slowly deteriorating!
Under a true Bortle Class 1 sky the conditions are indeed so striking in the number of stars visible to the unaided eye that for most of us the general constellation outlines are all but lost against the background density of fainter stars. Likewise, individual faint stars to magnitude 7.5 , or better, can be detected by those with 20/20 vision and DSO like M33 are clearly naked eye objects. This is a fact that I can fully attest to, since I lived under such skies for more than a decade.
Definitely Air Glow is not the culprit to what you are reporting as a general sky glow and the solar cycle is on the down-turn anyway and Air Glow pretty much is situated within ~15 degrees of the horizon.
I do note that a number of West Coast observers are reporting that jet contrails are increasingly becoming very troublesome, the individual trails diffusing to merge into a vast sheet of very thin cirrus-like structure over the entire sky. If this is drifting eastward toward AZ and NM and finding even very widely separated light pollution sources it might be enough to account for what you report.
The above is about the best suggesting that I can offer, at least beyond the simple spread of universally growing light pollution (urban sprawl) as the U.S. population steadily increases, particularly in the American Southwest.
J.Bortle (BRJ)