One thing that is not mentioned here is that often it's not a direct connection.

My family were refugees from the Soviet invasion of Afghanistan.

The USSR tried to claim that Afghanistan belonged to them, so the US didn't want to go directly into Afghanistan.

As a result the US went to small rural villages in Pakistan just across the border in Pakistan. They gave these villagers excellent weapons and lots of money and told them "take these to Afghanistan so they can fight the Russians". This was called Operation Cyclone: https://en.wikipedia.org/wiki/Operation_Cyclone

These people took some of it, and kept some of it. When the war with Afghanistan finally bankrupted the USSR, these people who kept the money and weapons then supported the Taliban and they used the American weapons to take over the country.

America has generally been reductant to admit that the Taliban has effective weapons so we often have to look at foreign media to get around US propaganda.

For example in British media, they show that the Taliban used American anti-aircraft missile systems to take down American aircraft: https://www.theguardian.com/world/2010/jul/25/afghanistan-taliban-missile-strike-chinook

Meanwhile the American government wants to insist that leftover equipment is fully disabled. And that the Taliban are too stupid to use it.

If the Taliban know how to operate American missile systems, they could probably rebuild a few Humvees.

One of the biggest problems I see with Americans is they like to connect evil with stupidity.

There's no reason you can't have an evil genius. If Hitler was stupid, the Holocaust wouldn't have happened.

In 2015-2016 countless people said Trump was too stupid and it's impossible for him to become president.These people were too naive.

Underestimating evil entities is a very serious issue.

Nonetheless, the US likely gives Ukraine lots of stuff indirectly through neighboring countries.

If the US had a significant presence in Ukraine - that could cause a direct conflict with Russia.

If Russia kills a US soldier in Ukraine, that can now cause a messy situation.