The issue is that 1000x the economy doesn't help one bit unless you can use that economy to produce matériels. Currently, Russia's production capacity for e.g. artillery shells is estimated to be larger than Europes.

We're actively seeing in Ukraine that throwing cannon fodder at troops that are running low on ammo is a viable strategy if you can eat the losses, which Russia appears to be able to do.

Of course, I believe that Europe would be able to get its shot together and scale up weapons production if attacked. At the same time, I believe that while we are scaling up production, we would need to plug gaps in the line with bodies. In short: Do we really want to lose a bunch of people just because we waited to increase production until we were attacked?

Also, I think Europe should be capable of defending itself without the US. Having the US as an ally should be a bonus on top of already being a force capable of beating Russia.