That's changing, but for many years European nations did not spend very much on their militaries. A large part of why is the protection of NATO and US bases in various countries.
Europe has spent less on military because after the cold war and still today, it never had any realistic threat. Russia can't even take few miles off Ukraine.
The only realistic threat is the US, which is an ally, in theory. Now a threat.
The realistic threat is Russia, which is currently winning a war in Ukraine through sheer attrition and will succeed unless Europe steps up big time.
I hate Trump and would much rather see the world keep on going the way it has been, but Europe's militaries grew around an American core after WWII. A few nations have serious armies (France, for one) but most of Europe is close enough to a US airbase for a small military to work fine.
This misses the point, which is that Europe and the US need each other. Without the US, Europe stands no chance against Chinese and Russian influence. Without Europe, the US cannot stand against China and Russia.
And yet Europe is unable to support Ukraine enough to change the course of war.
Which is the direct cause of the current situation. If Europe was so strong and ready, war in Ukraine would be over, Russia was defeated, and US wouldn't even think of doing what it is doing.
Everything else is copium.
It's not unable. There is little political will in Europe and USA to support Ukraine with arms to the victory. They support Ukraine just enough to not loose. It's in their interest to grind russian meat and tanks in Ukraine as long as possible.
That's the wrong comparison - the comparison in this context is the size of the European military versus Russia.
Is it just me that finds it odd that the same people say that both Russian is an imminent threat to Europe - where its tanks could roll over the continent - and at the same time say just one more push to win in Ukraine?
If Russia attacked a united Europe it would lose - the slow defeat in Ukraine is purely a matter of will, not capability. ie it matters more to Russia than Europe.
Note most Europeans don't see the war in Ukraine as an attack on Europe by the Russians - despite what the hawks would like to paint - that's why the hawks can't bounce Europeans to put significant boots on the ground in Ukraine.
The US spending could be the result of so many other factors.