It takes more than math for your doomsday scenario to pass muster.
I've done the math on this (I'm not the poster you were talking to, but I know what I'm doing with these models), and it's not pretty here either. If it spreads beyond very small numbers, as in 100 or so undiagnosed infected individuals, it will be very hard to wipe out without crushing our economy in a way that you don't want to imagine. Our doubling time start at 40-60 days, which is much better than Africa, but it could easily get ugly here too.