Dont forge that a lot of that red space is cattle, lakes, mountains and most importantly...no people. The election map gives a distorted view for both GOP and Dems. For example take Virginia, with a small sliver of blue in that sea of red. Well the population of the blue there is maybe hundreds of thousands bigger than the rest of the red portions. Los Angeles alone has more people than those square northern states combined.
The key for 2020 is who is going to maintain the lead in the southern cities and mid west.