One of my biggest pet peeves when I hear politician and pundits talk about threats to US or Canadian or whatever security, the phrase existential threat is often stretched to the point of meaninglessness. There are many threats to security, and they range from minor/modest to severe to, ultimately, existential.
Climate change might be an existential threat to low lying island countries such as the Maldives. It is not an existential threat to the US or Canada. Sorry, it just isn't. Something that presents significant harm does not threaten the existence of the United States or Canada.
Nuclear annihilation is an existential threat. Which is why I concurred with General Dunford in his testimony today when he said Russia is an existential threat. Why? Russia has enough nuclear weapons to lay waste to North America AND our relations are such that we have more than a just a bit of concern. Putin has been making nuclear threats to American allies--ones where the US has a commitment to defend. That defense is ultimately tied to a nuclear umbrella. So, yeah, Russia is an existential threat. France has enough nuclear weapons to destroy the U.S., but is not a threat, existential or otherwise.
China has enough nuclear weapons at this point that it is probably an existential threat as well. Right now, its assertiveness is troubling, and could start a process that could lead to things getting out of control. But China is not issuing nuclear threats left and right.
Iran is not an existential threat to the US or Canada. Even if Iran had a handful of nuclear weapons, they would not have a delivery system that would pose an existential threat to the US. Ye olde feare of a nuke in a suitcase is not an existential threat--again, harm is not equal to threatening existence. Sure, it would be an existential threat to Israel, but that is distinct from being an existential threat to the US. How is this different from Russia's threat to the Baltics? Iran ain't Russia, and the US does not have an Article V type treaty with Israel.
Cyber? Costly, inconvenient but not existential unless the hackers can turn the computers into Terminators.
Terrorism? ISIS? Not existential threats. Even if ISIS were able to get its hands on a nuclear weapon, that would not be an existential threat. The threat to the existence of some people (say, residents of NYC) is not the same as the threat to the existence of the US.
Alien invasion? Well, if they have the aims of those depicted in Independence Day, then yes, that would be an existential threat. A meteor of sufficient size to lay waste to the planet? Hell yes!
So, we need to address the serious threats, such as cyber stuff and Iran and climate change, but we need to keep things in perspective: they don't threaten the existence of the US or Canada. Calling them existential threats is fear-mongering. We have enough to be concerned about without inflating threats. That is how we got into Iraq in the first place, more or less.