I don't know if Ukraine can actually win or not - throwing Russia completely out. Not unless they get an air force and/or Putin gets killed.
The US, imo, should be pushing for making Donbas and Crimea non-militarized zones, under control of Ukraine, with UN forces occupying those areas. This would give Russia the security it claims it needs and Ukraine gets to keep its national soveignty intact
Until then, we need to keep funding Ukraine because, if Russia does win, we'll be doing this all over again in 10 years. But, as Trump said, we need to insist that NATO countries step up their support of Ukraine.
The wild cards, to me, are Putin's hold on his dictatorship and whether or not Ukraine gets advanced weaponry, i.e. jets and longer-range artillery.