Transition to one-party-system

[Stranger in a strange land]

Even if you dismiss all the pitfalls of any one-party system, a US one would be particularly horrible because it would give that much more power to the Iowa caucuses.

Er, the Iowa Caucus is far less relevant than it used to be these days: SC is much more important on the Dem side (because it effectively gives Black voters a veto over the nominee), and increasingly so on the GOP side.