Putin might not choose to use a nuclear response but that doesnt mean a nuclear response is impossible. For one it's now a legal order to use a nuclear response to conventional attacks inside the Russian chain of command. Theres a zillion scenarios where Putin doesnt even have to be in the loop...
The historic Russian strength has also been theres more where that came from.
Manpower isn't just infantry strength it also equals military production strength.
Over the course of that 3 years the US/EU were telling Zelensky not to talk to Russia and were keeping Ukraine in the fight with NATO carrot. Just beat Russia and youre in!
US is absolutely shafting Ukraine here, but at same time ending this war is better than escalating with the Russians...