Roughly speaking (+/- a few % or so), about half the population of the US is on one side and half on the other side. Neither group of the bifurcated population is small.
Well, that map was showing more like 60/40. But I suspect are large number of those blue votes were disaffected Republicans who voted Blue to get rid of Trump. I know the feeling.

All in all I'll agree with your assessment. But certainly not what what's his name was trying to imply and not what Trumpers are trying to imply every time they wave the red map around. "Look! See how many of these squares of empty desolate space devoid of human habitation we colored red??? MAGA!"
But really, that is only a smaller part of the story.
The real story is what is the 10 year trend look like?