You may (and physically can) only overtake when there are two lanes going in your direction. The road alternates every couple of km between 1 and 2 lanes in each direction.
I think this 2+1 wouldn't work in the US because (in my experience) very few people use the lanes correctly and they just distribute themselves evenly across all lanes, regardless of speed. That strategy does, indeed, lead to bottlenecks when the number of lanes reduces.
Similarly you can't really bottleneck because the only input is a single-lane road - they're not long enough to add anything more than trivial traffic in rural areas.
The big benefit I see is that you're never entering the opposing traffic lane, so head-on collisions are much less likely.