I see the RF we're dealing with today as a result of it being an empire of disparate peoples that need to be kept under control - and that empire as a result of the geography. Flat land with no defensible borders means a horde can sweep through. Low per-area productivity means there isn't a large enough population to stop that horde. So expansion to defensible borders, subjugation of conquered peoples.

As long as it's an empire of peoples that needs an internal army to keep control, democracy just isn't possible. The only option is to let it expend its military age population - so whatever strongman that comes to power won't have the option of attacking.

Also: if it does fracture, I'd suggest that putting the US in charge of 'nation building' is an exquisitely bad idea - but probably how it will go.

Just my $0.02.