Flag theory is more tailored towards geopolitical risk hedging; it's great to have an option to easily be able to enter a new region of the world without being questioned due to your nationality during a time of crisis.
Discussion
Yeah it’s a half decent theory, but it often doesn’t play out that way if you didn’t have good opsec/privacy. If the American government wants another nation to deny someone entry they usually will. They commonly ask for those on watch lists or criminal investigations to have their movements restricted and this is usually honored. An extreme but illustrative example was Pablo Escobar’s family was unable to travel internationally at the request of the US government. In a time of crisis the US government can easily just declare an emergency and close borders.
This CAN work, but it requires both good enough opsec that the American security state hasn’t flagged you as someone of importance and leaving before that crisis is in full swing.
And even if you have successfully traveled somewhere, most nations will still adhere to American extradition requests.
However this is written from an American perspective. If someone is from a country that has less international power projection I can see this as viable.