The US has every incentive to turn Ukraine into Russia’s Vietnam.

Biden took the approach of keeping 10 pairs of gloves on when dealing with Russia. Don't help too little not to make it too easy for the russians, don't help to much to avoid escalation.

I understand and agree with that. But you said "With a heftier backing from the US the Russo-Ukrainian war would be over by now.".

If that was viable, why would Biden not have done so during the years he had?