So you think that Ukraine being overrun is a negotiating card? For whom? Why does America care? It's really Europe's problem, and Europe is not united enough to mount the necessary response. The reality is that Europe has underfunded their defense to the tune of trillions of dollars since the fall of the Soviet Union, and if Ukraine really mattered to them then they would have started investing in their defense back in 2014 when Crimea was "overrun" (and there were basically no consequences whatsoever). The EU's GDP is 10x Russia's; if it's really so important that Ukraine wins, then let Europe fight!
Russia conquering Ukraine will bolster the Russian economy and incentivises then (as well as China) to continue territorial expansions. Already the war has given rise to military and economic alliance between Russia, Iran, North Korea and potentially China. If things continue in this direction, it will absolutely become a big problem for the US. Better to stop the rot asap.
Oh, but they do. We (the west) can't allow them to be overrun.
So if they refuse to accept a deal, what can we really do?
Starving Ukraine for supplies would be extremely dangerous.
(That said: I'm not sure Trump understands this)