A statistician named Ryne Rohla who writes at Decision Desk HQ, has compiled a precinct-by-precinct map of who won in the 2016 presidential election. He also has maps for 2012 and 2008 if you want to compare. Hat tip to Instapundit for the link.
Colored red (Republican) and blue (Democrat) his maps make excruciatingly clear how little geography is dominated by Democrats. The only truly large geographic areas of blue are where most of the population is Native American, Latino, or African-American.
Literally the two big blue regions are first, the so-called "Big Res" of the Navaho which sprawls across northeastern AZ and northwestern NM, and the adjacent reservations of the Hopi and Zuni located in those two states plus the adjacent Ute in southern CO.
Second, blue dominates interior Alaska which isn't a reservation but is mostly populated by native peoples at very low density. And there is a substantial, though smaller, area of largely Hispanic people in far southern TX.
There is also a string of "blue measles" across the interior deep South. These represent pockets of predominantly African-American population.
A cynic would look at this map and conclude the Democrat strategy of reliance on minority voters was much of what they had going for them in 2016. Rohla's map says "tribal politics" in a very graphic way.