If the Europeans aren't preparing to ship huge amounts of material aid to Ukraine, then they are sleeping at the switch. Given the way Germany insisted on refighting WWII in Yugoslavia, I think the odds of Germany not helping Ukraine are zero. We'll see. For Poland, this is an existential crisis - Ukraine's territorial is essential for Poland's national security. Do the Poles really believe Uncle Sam will fight to keep Poland free from its former Russian overlord? Just in case, it's better to have a unitary Ukraine, which can be had on the cheap by providing a equipment to Ukrainians willing to the pay the price for freedom.
If Lviv/Lwow were threatened by the Russians, the Poles will move in first, I guarantee that.