US had been there for 20 years. The same think that happen in Vietnam when the US left.
The US supported regime could not hold the countries after they left
Bush and the US got involved because of 9/11 and to punish the Taliban. That is the only reason the US got involved
I don't have a problem. If the Afghan or South Vietnam people cannot hold the country then there is no reason for the US to hold it for them. You can only be be involved for a short period and will eventually have to leave. It is a no win situation that did cost American lives.
At one time the US had 100,000 troops in the country. it dropped to about 8,000 who were mostly doing training before the decision to withdraw completely.
Still in
2/2000 Trump reduced troop levels to its current level.
He also committed a 2/2020 agreement with the taliban for a full military withdrawal from Afghanistan by May 2021
In a
February 2020 agreement with the Taliban, the US committed to a full military withdrawal from Afghanistan by May 1, 2021.
This is what Trump agreed to and Biden decision was to carry it out or keep the troops there. So if Trump was still president, the troops would have been withdrawn.