It sounds to me like you're positing the GOP stops playing for White Southerners. The only alternative I can imagine is dumping the vast majority of their money into the midwest/north and southwest, with hopes of massively improving their share among hispanic voters while maxing out the white vote outside of the south.
If that started in 2016, maybe following this whole flag thing, you'd still see some of the strongest Republican southern states staying Atlas blue just out of inertia. But we're assuming the GOP refuses to spend significantly in the region, so a lot of the Democratic stretch goals like Georgia fall. Meanwhile, the GOP might be able to make a few gains outside the south, but over all this is a big Democratic victory. Something like the below.
After sustaining this message for four years, hispanics and non-southern whites might start to take the GOP more seriously. This map might be possible in 2020.
That's a 290-248 Democratic victory. The problem for the GOP is an overall drop in white voter turnout in the south which makes states like Mississippi, Georgia, and North Carolina, which should be in play, difficult mountains to climb. I have a hard time seeing where the GOP could go from here, unless it completely reinvented itself in order to be competitive within cities.
