I don’t see how the US could possibly be the one precenting a diplomatic solution in Ukraine? Russia continues to presue maximum war aims, including having officially amexed whole regions into the the Russian Federation that has not at any point in the conflict been held by Russia, and maintaining that any peace not only mandates that Ukraine can not at any point in the future join any defensive alliance or pact but also that Ukraine stops holding elections in favor of its leaders being appointed solely by Moscow.
The territory thing is important because the Ukrainian constitution specifically requires that any change in the nations borders be approved by a public referendum in which all citizens can vote. Given that current polling shows about 2 to 4 percent support for such a referendum, such a deal is unlikely to be approved anytime soon.
Militarily, it is important to note that the Russian government is not and has never been the Soviet Union. The Soviet Union’s was an alliance of dozens of nations where the majority of its military production were in nations like Ukraine, Germany, and Poland. Russia has large reserves of Soviet equipment in fields that it has been rebuilding, but a limited ability to produce fully new equipment. Hence why for instance they are buying up large portions of the North Korean ammunition stockpiles to make up for a lack of domestic supply.
On the other hand, Ukraine’s production is in the other hundred and ninty some odd nations that make up the gobal economy. Supporting it has made up a relatively small percentage of that economy, which is why in 2023 for instance the US provided over twice as many old tanks to Romania alone than it did to Ukraine. More importantly, the US can build thouse new tanks without starting by pulling a rusted shell out of a field first.
Given that at the current rate of Russian advancement it will take them decades to get back to where they were a few years ago, and over a century to fully concur all of Ukraine, the general strategy has been to let the dictator burn though his stockpiles and foreign exchange reserves while training the Ukrainians on stuff like tanks and air defense that entered production after the fall of Soviet Union.