This is not the first place I’ve seen the “starve out the cities!” scenario suggested, and it still seems unrealistic. If it’s a voluntary boycott, then the Trumpist areas destroy themselves economically because they aren’t selling the food, goods or providing labour they normally do to earn a living. In other words a farmer that voted Trump and doesn’t sell his crops in order to starve out the cities might easily feed his family and neighbors and give the rest of it away, assuming those crops aren’t left to rot in the fields, but he won’t be earning any money either to pay off loans or buy seed. If the scarcity is the result of an insurgency that actively prevents rural goods from reaching urban areas (as has been suggested elsewhere) then the insurgents are most directly harming the rural population they presumably live among and will quickly lose popular support. And practically, enough food and other goods can like be supplied from foreign sources or even domestic food-producing areas that remain loyal. And many areas could be at least neutral enough to capitalize economically from the situation (as the artificial scarcity will inflate prices). So, as you say, in the event of an Impeachment the Trumpists will likely remove themselves from the American political system by checking out, and then the US economy as well. If they start an insurgency, the one population they will hurt the most is the one most sympathetic to them.