But a large degree of the exception was being excepted from being blown to smithereens during WW2, which is the kind of opportunity that doesn't usually come around twice.
> doesn't usually come around twice.
There is a _2_ in WW2 :)
Sadly looking at history these "opportunities" come around quite regularly.
Big beautiful oceans
> which is the kind of opportunity that doesn't usually come around twice.
On the contrary, it most definitely did come around twice (hence the 2), and those same geographic advantages are still at play, barring thermonuclear war. It wasn't pure chance that Europe combusted in WW2, Europe had been on fire off and on for hundreds of years. Its geography just lends itself to large scale conflict.
The recent period of peace is an exception, but it's not the first exception and there's good reason to suppose this one won't last forever either.