1. America used to have open ballots, about 40 years after Australia had the secret ballot, America got them.
2. If one party consistently gets beaten because a third party undermines its support (see: Bush running ads for Nader in Oregon) then that defeated party will rationally favor an advanced voting system.
3. Every third party would naturally favor it, and currently allegiance to the two parties is below average.
4. Voting happens at the State level. Vermont has already adopted, temporarily, a ranked ballot system. It was used in the Mayor's race for Burlington. The not greatly popular Democrat was not sunk by the Progressive.
5. It's rational. Sorry, but the fact that 2,000 years ago the Romans had a more sophisticated voting system than modern Americans sucks.
By the way, Condorcet was a friend of Thomas Jefferson's. Jefferson spent a lot of time in salons in Paris, including Condorcet's, plotting the French Revolution.