You are quite correct. So why can't Europe defend itself?
Now apply that logic to Europe. Why aren't they doing more to support Ukraine? Why don't they give Ukraine the weapons and money necessary to win? As you pointed out, Europe has the economic muscle to dominate Russia, if it should choose to do so. Why aren't they?
Except that they ARE. I have no idea why you continue with this lie that they haven't increased military spending. That is actually one thing that almost all Americans did actually agree with Trump on. Yes. Europe should have been spending more on their militaries than they have in the past. And even the European governments themselves have agreed with that as well. Which is why they have increased their spending on their militaries by several percentage points of GDP.
As a matter of fact, the fact that they haven't spent as much on their militaries in the past as the US has per capita, is actually a good thing. As I've said in that long post, investment is a good thing. Europe spent a lot of their time and resources building their economic base up for all of those decades post-WWII. Now, here in the mid-2020s, that has borne fruit. (As a matter of fact, the phrase "borne fruit" is a great analogy, and one that the Bible even uses at least once. A farmer expends his personal energy plowing in early spring, planting in early summer, and harvesting in the fall. He "reaps what he sows," as the return on that expended energy is a hell of a lot more energy he and his family can consume and even sell at market at a profit!)
Europe is a superpower unto itself. As a supra-national organization, Europe has 6 carriers (that includes 2 British carriers). China only has 3, with a fourth under construction. China has over a billion in population. Europe: 400 million. China has nearly 3 TIMES the population of Europe and a ◊◊◊◊◊◊◊◊ more natural resources. And yet, Europe by itself can project more power than China can. And this doesn't even include the 11 carriers the United States has by itself.
Why talk about carriers? Because it shows force projection. Obviously, number of carriers itself doesn't tell the entire story. But it is a vital marker to use to show the manufacturing capabilities of nations and supra-nations. The ability to bring a ◊◊◊◊◊◊◊◊ of resources, labor, and infrastructure to bear in order to build massive platforms of firepower that can be floated to any point in the world. As well as all of the support vessels and equipment to surround these floating fortresses in a bubble of protection.
Furthermore, the fact that Europe has always had civilian factories churning out cars and other products, makes it particularly easy to retool those factories and churn out military vehicles and ammunition instead. The United States famously did that during WWII. Europe has also invested VERY heavily in alternate sources of transportation, rather than rely solely on superhighways. Unlike here in the States where the extreme right wing MAGA-cult has increasingly been critical of investing in such infrastructure. Not even into our highways, never mind proposing the construction of more railway! Taxation, especially of the super wealthy where 95% of the entire nation's private wealth lies, is completely out of the question, and they are even demanding MORE tax cuts for these people, even as they cry about the amount of debt that's been piling up! It's absolute madness!
But yes. In the end, Europe HAS been supplying Ukraine. But that dopesn't mean they can take up the slack of the United States pulling out in supplying Ukraine. Obviously, when you subtract something from a hole, you will ALWAYS have less of that something. Like a pie. Even if the United States only provided 25% of the total equipment sent to Ukraine, that still 25% less that would be received and used against a dangerous rogue terror state like Russia. If you've played any Paradox games like Europa Universalis, when the city-state of Ulm sends a measly single regiment of 1,000 troops to attach to your main army, that's still 1,000 more troops than you otherwise would have had. And if Ulm decides to withdraw those 1,000 troops from your arm, that's now 1,000 fewer troops that you now have and you can't replace them.. Like:
Europe and the USA combined have nearly 3 quarters of a BILLION in population. If you subtract the 350 million Americans from that equation, Europe cannot just magically pull 350,000,000 more people out of their rear-ends. When you combine what Europe produces with what the United States produces, it will ALWAYS be more than what Europe produces alone, or what the USA produces alone. That's literally how basic math works, and we learn that when we are, like, 3 years old.