Putin wants a Ukraine that is completely subservient to it. Ukraine wants to retain its independence and sovereignty. All the "deals" that the US talks about are ones that hand Russia its war aims: a rump Ukraine without any plausible guarantee that Russia will not resume attacks. If Russia can resume attacks at any time, it can pressure Ukraine into adopting policies favourable to Russia, instead of those in Ukraine's best interests; in other words Ukraine will be subservient to Russia and not be sovereign.
It's basically as simple as that: why would Ukraine stop fighting, and even grant concessions to Russia like territory it hasn't managed to conquer, in order to become a puppet regime of Russia, the very thing it has been trying to resist this entire time? The only reason would be if they are unable to continue fighting effectively and so have to choose between a slow, damaging defeat and a cleaner surrender. But this isn't the case! The fight has been more or less in a stalemate for ages.
Too many people, including in governments, do not understand (or are just unwilling to recognise) that it is about a fight for sovereignty, not a question of how much territory Russia gets in the end. If Ukraine is left unable to, for example, pursue a closer relationship with the EU because of the threat of Russian aggression, is left susceptible to Russification through Russian propaganda so that Ukrainian culture risks being snuffed out, there is no point in doing a deal.
It'd be like if there was someone in your house who has just beaten you up and says if you ever so much as speak to Barbara again he'll kill you, and the police come and say "look, just give him your wallet and both of you stop fighting!"