I think you're 1/3 right on this one. The US definitely wants the Russian forces fixed in Ukraine as long as possible. That is the 1/3 you got right.
The US spent billions and 8 years training Ukraine's forces and hardening defenses, particularly around the Donbas. Thus the very slow progress of the Russians. But progress it is.
Anyone who listens to military experts NOT intent on just saying the Ukrainians are winning must admit the Russians did not send enough forces to take either first Kyiv or now Karkov. These are fixing operations that have worked very well to keep Ukrainian forces from reinforcing the troops in the Donbas. We'll never know if Russia actually believed they would drive in and the Ukrainians would see them as liberators (a la our deluded belief going into Iraq). But the give and take around Kyiv has cost Russia little in men and equipment (compared to what they have in reserve) while tying up Ukraine's forces for 3 months now.
That fixing operation lead to their victory in Mariupol (now estimated at 2000 POWs not 250 as first reported), and now multiple Ukrainian platoons surrendering in the Donbas. Russia is close to encircling the Ukrainian forces around Lysychansk. That would be a major victory like Mariupol and Kherson. If Russia wins there they will be on their way to doing the same in Kramatorsk. Then they would have the Donbas, a landbridge, and the possibility to move those troops towards Odesa.
This is the same slow methodical process Russia used in Syria. The only thing that stopped a total Russian victory there was the US illegally occupying 1/3 of Syria (that is a war crime, by the way).
That second 1/3 you got wrong (or at least the NATO people you linked to did).
The Ukrainians are not going to be allowed to give up, even when it is clear they can't win. Our MIC makes too much money for that.
The third 1/3 you get wrong is that Russia gets a huge advantage out of this: Practical experience fighting NATO. We have been training and supplying Ukraine to NATO standards for 8 years. We've trained 10s of thousands of Ukrainian troops on NATO methods and weapons.
Win or lose, Russia knows how to fight NATO, and they still have huge armed forces that have not been involved in Ukraine. Our military experience since the 90s has only been fighting vastly inferior armies.
