>They can build up a force capable of annexing the strip of land between Belarus and Kaliningrad.
Ok, I'll take this as a starting point. Let's assume Russia has committed to seizing everything south of Kaunas and Vilnius, and north of Suwalki. The eastern part of this patch of land is ~200km frontage with Belarus (south of the E28 Highway). Because Kaunas and Vilnius combined have populations of ~900k, I'm going to assume the Russians will aim to bypass rather than seize them, so that will involve establishing blocking positions south of both cities in order to isolate them from the desired terrain. It also involves capturing Alytus, about the same size and population as Bakhmut. I would need to dig through some doctrinal publications to figure out how the Russians would template a force package for this op, but I'll spitball it at at least an entire corps/Combined Arms Army of 2-3 divisions and a few separate brigades, maybe 60-80,000 men?
While the focus is on repulsing an attack in this southern sector, let's assume Lithuania fortifies the entire border with Belarus, which is ~350km. Minefields 1km deep with 1 AT or 1 AP mine per 6 square meters would require ~60 million mines and $5 billion USD (about 1 year of Lithuania's military budget). That's an extreme lift but not impossible if amortized over several years, even without help from other EU nations. A defensive belt built behind a minefield like that will take the Russians weeks to penetrate if properly supported by other assets. Those weeks give the rest of the EU decision space for political action as well as time for mobilization/flowing combat power into the Area of Operations.
So the real question is "why"? Why would Russia want to expend the resources to accomplish this? Figure out what Russia wants and then structure a defense that imposes an unpalatable cost on the attacker. My position is that it can be accomplished without American involvement. Finland spent the Cold War a) outside of NATO b) with no independent "security guarantees" c) without getting invaded by the Soviets (again).....because it also made itself expensive enough to invade/annex that the Soviets didn't think the cost of re-absorbing that particular bit of formerly-Russian-Imperial-territory to be worth it. Facing down a massive conventional military assault from a well-equipped and supported adversary is not impossible: the Lebanese have done it twice in the past twenty years against the Israelis. Be like Lebanon.
>by committing to re-arming now and providing everything we have to help Ukraine kick Russia out of their country - a full rout of the Russians
That's not realistic. At all. There is no reality where Ukraine forcibly ejects Russia from the land bridge that it has established with Crimea. Breaching Russia's fortifications requires more combat engineering equipment than exists in all of NATO at this point. The Ukrainian 2023 offensive was supposed to reach Tokmak in 3 days. It took them closer to 90 days to even breach the 2nd of 3 defensive lines north of the city. Let alone actually reach Melitopol and Berdiansk. No army on the planet is trained and equipped to deal with kilometer-deep defensive belts covered by artillery, UAVs, attack helicopters....AND enemy air superiority. You would need to completely collapse the Russian army and economy 1917-style, which is also not looking likely, or at least not likely to occur before Ukraine itself collapses.
At some point Europeans need to come back to reality. Until then.....Americans are no longer interested in getting tangled up in Europe's mess (even though the mess is largely our fault).
> So re-arming such that we have complete independence from the US reduces their leverage.
Which ironically is what Trump wanted Europe to do anyway: pay for your own security with your own money!
> In a good timeline having both a strong Europe and strong US on the same side puts us in a very good place wrt China / India etc in the future.
The US is returning to a Pacific focus, like the one we had 1890-1913 (ish). I think this is the correct posture for us. We don't need to be on the "same side" of Europe, just like we weren't really on any European side until Woodrow Wilson, America's worst President, ruined everything by getting us into WW1. Due to geography we are fundamentally a maritime power, and we should be focused on trans-Pacific trade with the growing economic heart of the planet: the Valerierpieris Circle ( https://en.wikipedia.org/wiki/Valeriepieris_circle ).
Hopefully my post isn't too disjointed and rambly...