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and Russia would have never invaded. We, the West, committed to defend Ukraine in exchange for its denuclearization so there is no need for Ukraine to thank the U.S. for keeping its promises. See https://www.armscontrol.org/factsheets/ukraine-nuclear-weapons-and-security-assurances-glance
Secondly, Ukraine is defending not just its own territorial integrity but the future of Europe. I have been interviewing people from the Russian-occupied territories the last few weeks and they really do live in a Stalinist prison camp that is unbelievably oppressive.