The problem of Afghanistan has never been conquering it, but holding it, the Soviets ran into the same issue. Anyway, the km's really do matter, if people truly fear for a deeper invasion into Europe.

I don't think it's a convincing narrative that that's what Putin wants, and also that that's something he could reasonably accomplish. But I do hear it often as a powerful narrative to help Ukraine more, and I understand why, but from my point of view it's not very convincing.

At the same time I agree with the sentiment that heavier the losses in Ukraine, the more he will have difficulties in starting similar drama in other countries with large Russian communities.

As it turns out, glassing an entire country is politically unpopular.

Unless you're Israel

The US occupied the country for 20 years. Staying just became unpopular. The US lost about as many troops in 20 years as Russia loses in 2 days of fighting in Ukraine.

The situation in Ukraine is not very comparable with the US occupation of Afghanistan. The US captured all of the major cities in Afghanistan in a matter of weeks, after which the Taliban were pushed into a sliver of southern Afghanistan and into Pakistan, which borders those Southern regions of Afghanistan. The issue, as the other commenter mentioned, was in holding the territory. This issue of maintaining stability was worsened by how the US both ignored the Taliban's attempts to negotiate early in the occupation and ignored the fact that the Taliban were being harbored in Pakistan (which was considered an ally), allowing the Taliban to regain strength. Had the US targeted objectives in Pakistan in the early 2000s when the Taliban were weak, rather than waiting till 2011, history may have turned out differently.