Actually, it very much is our fault. This all started at the end of WW2 mind you.
NATO exists because Europe was in shambles and didn't want Russia to seize the continent. Russia was also concerned about potential invasions. In all that time Russia's sovereignty was being encroached upon while Ukraine allowed terrorists and spies to have free reign. Ukraine made a very bad situation worse for themselves. Further, Russia, China, and OPEC want to break our hold over the petrol dollar and reserve currency status. By getting involved in this, at precisely the wrong time, we ignore our own weakening military, tech, infrastructure, and government. Which means when the dam breaks, USA isn't going to have a good time. This isn't like before, we are no longer a singular nuclear armed superpower.
Save our allies from hostile annexation? Yeah, we are doin a bang up job at it. Money, weapons, supplies, billions of dollars worth and less than half actually made it to Ukraine. Half of our "allies" including Ukraine are straight using our charity to grift us. Meanwhile, our own citizens are overworked, underpaid, our social nets are crumbling, an attempted coup by theocrats and autocrats is under way, the homeless population is exploding, women, trans, and homosexual are losing their rights. But let's worry about Ukraine's corrupt government surviving because we want to monopolize European resources.