My recollection of the exit from Afghanistan - we were assured the Afghan army, having been trained and equipped by the west would be able to maintain order.
It is not clear whether this was a smokescreen intended to make withdrawal politically "palatable" - did the US expect the army to collapse in just a few weeks as the Taliban advanced.
More fundamental - I struggle to think of major conflicts over the last 70 years involving the West and in particular the US that have been successful in "righting a wrong" - evidenced by a fundamental long term change in circumstances.
Forays into the Middle East - Iraq, Afghanistan are demonstrable failures which have destabilised the region - in particular Syria. Vietnam ended in retreat and defeat. North Korea still a rogue state. Any other major operations I have missed?
Successes - the US managed to invade Grenada, UK won back and retained the Falklands. Former republic of Yugoslavia had some hands on involvement of US and UK but mainly air support.
The lesson - perhaps power through military means is no longer the best option. Support - weapons and intelligence - for Ukraine is right, active involvement on the ground would be an indefinite commitment with no certainty of success.
What has this to do with Trump/Biden - dialogue and economic power may be far more effective than conventional military solutions. China, now the equal of US in global reach, have achieved success substantially through economic means - trade, building infrastructure etc etc.
Trump (IMHO a reprehensible individual) seems able to maintain a dialogue with Putin, Kim, etc - possibly even an Ayatollah! Subtlety is not one of his strengths - success in resolving current conflicts may benefit from the simplistic and direct where conventional politics fails.