https://www.theatlantic.com/ideas/archive/2022/08/us-russia-conflict-ukraine-war-afghanistan/671065/

An interesting IDEA article on American thinking while fighting the Afghan War. Basically, a war of option. In short, the author of theAtlantic.com article identifies several elements pervading features and how Russia strategists seem to be capitalize on these peculiaity.

1. "A saying in the Afghan War was that the Americans had the watches, but the Taliban had the time. The point wasn’t necessarily that Americans should have fought longer, but that we were always publicly looking for an exit. Indeed, in the 20-year conflict, we were never more than 24 months from an announced troop drawdown.
....
Russian strategists, alert to the U.S.-Taliban dynamic in Afghanistan, understand that the key to outmaneuvering your adversary in time is convincing him that you have more of it. "

2. "In Afghanistan, America too often sidelined NATO member nations. From President Donald Trump’s direct negotiations with the Taliban to President Joe Biden’s uncoordinated withdrawal, American unilateralism eroded NATO credibility in Afghanistan, weakening the alliance. And the chaotic withdrawal from Afghanistan marked one of NATO’s darkest moments.
In Ukraine, Russia will be looking for opportunities to precipitate the type of NATO dysfunctionality that characterized events in Afghanistan one year ago. The Russians also know that their success in Ukraine will not hinge on their ability to cultivate proxies—such as Belarus—but on their ability to cultivate partners, particularly China."

3. "Putin’s continued insistence on classifying the largest war fought in Europe since the Second World War as a “special military operation” shows his political vulnerability to excessive Russian bloodshed. America’s political class effectively waged the Afghan War within the recesses of America’s consciousness. The outcome of the war in Ukraine may well depend on Putin’s ability to do the same."

But then, US was fighting a war of option in Afghan. It did cost the US tremendous money and energy. But the war is in no way existential. The US is certainly not exhibiting above features in its dealing with China regarding Taiwan.