This is what it means to be a liberal Progressive: a violent, transnational Islamic radicalism that preaches world conquest and death to unbelievers is not an existential threat.... but "global warming" is.
Well.... he's sort of right, actually.
An "existential threat" is one that, if threat becomes reality, destroys the object of the threat. The Civil War could be called an existential threat (it obviously was to the Confederacy). The national debt could well become an existential threat. WWII was an existential threat to most of the nations involved in it (less so the US, unless and until Britain and Russia were to fall).
Whereas occasional terrorist attacks, while terrible, would not cause the US to collapse.
Where Biden is wrong, is in leaving the discussion at the level of "terrorism," without actually going to the trouble of identifying who is doing the terrorism, and why. I can understand why he (and the rest of the left) are leery of tying "terrorism" to a certain brand of Islam: it would be wrong to condemn all Muslims for the actions of ISIS, for example -- and one of ISIS's goals is precisely to get us to use the broad brush against all Muslims.
But their avoidance of even mentioning "militant Islam" is a problem in itself, as it prevents us from (officially) engaging a dangerous enemy. The spread of militant Islam is not yet an existential threat. But (like Nazism) it could certainly become one if its spread is not acknowledged and checked.
