Probably because they spend less on the military and more on their people.

But would they be able to do that if they couldn't rely on US protection via NATO? If the US suddenly disappeared, would Europe be ripe for invasion by, say, Russia?

The European nations have been dealing with Russia since before there was an America, and it’s not clear that Russia would benefit from forced occupation of countries that don’t already have a large population that supported it. Irrespective of whether the Crimea annexation was legal, the population there already had a signification portion of people who supported it.

Russia trying to march into France or Germany, for instance, wouldn’t be a fun thing for anyone, including Russia.

Europe as a whole no.

Baltic states yes. Moscow views them as lost provinces with nontrivial Russian minorities, blocking land access to Kaliningrad.

France and the UK have a few hundred operational nukes. Even though Russia has more than a thousand, I doubt they’d risk it.

https://en.m.wikipedia.org/wiki/List_of_states_with_nuclear_...

Europeans do underspend on their own security, and Russia is a threat, but not quite in the 'all out invasion' sense.

But 'military spending' is a pretty small part of the 'difference between wealth creation' factors on either side of the Atlantic.

Against Russia, I'd back an Anglo-French-German alliance any day.

Surely you mean you'd back the defender?

NATO protection is a myth. Do you really believe the US would risk nuclear war with Russia just for Europe?

But why do you believe Russia would risk nuclear war just for Europe, what would they gain?

The first time NATO is not acting on it's obligations is the last day of NATO. Who need an alliance that does not work?

What did NATO do for the Greeks when Turkey invaded a good portion of Cyprus?

What do you they should do?

They do what they do because they have the US protecting them. Also, Liberty is taken for granted until you dont have it.