I don't have references handy but I believe China has evacuated well over a million people on several occasions for typhoons.

The major advantages they have are not so much "at gunpoint" but rather top-down organization, execution and responsibility, as well as a function railroad transport system for moving people. Also, the Lunar New Year festivities can see upwards of *100 million* people traveling - with many individual train stations used to dealing with over a million departures over a few days - so a million or two is no big deal other than inconvenient timing.

In the US evacuation planning and execution is entirely the individual state's responsibility. The federal government will provide as much help as the state will put up with, but the final decisions all rest with the state government. This can yield situations such as Katrina, where the governor did not even know she had an emergency plan, which pointed out such minor details as the fact that assisted-living facilities would need help evacuating patients.

The Katrina evacuation implemented by Louisianana amounted to asking people to figure out a way to leave on their own, which really isn't that different from how it's done anywhere else on the US coast. There simply aren't any systems here for moving large numbers of people inland other than private cars. In China they mass enormous numbers of trains in a short period, and top-down planning means the tracks will be clear and trains won't be hoarded elsewhere (here's where "at gunpoint" helps). Local organization means they know how many need transport, where they are, there's someone to count and make sure they all go, etc. And there is no arguing over individual rights when the Big Cheese says Go!