The Taliban has never been about attacking other countries, let alone the United States. It wants to control its own country and establish its version of Sharia law. It is enemies with ISIS-KP. Al Qaeda is its own entity, and while the Taliban may play nice with them, their agendas are different. The Taliban is not out for revenge but it will fight to protect its new government -- there, not here. As for whether they will allow al-Qaeda to rebuild training camps within its borders, that would happen with or without the Taliban. There are always going to be minor militant groups in Afghanistan.

The problem for Biden is that he has gone on record with ABC News among others and said he has no recollection of his military advisors disagreeing with his plan to withdraw troops from Afganistan:

In an interview with ABC News during the withdrawal, Biden maintained that he had no recollection that his military advisers had called for keeping troops in Afghanistan:

...GEORGE STEPHANOPOULOS: They didn’t tell you that they wanted troops to stay?
BIDEN: No. Not at — not in terms of whether we were going to get out in a time frame all troops. They didn’t argue against that.
STEPHANOPOULOS: So your military advisers did not tell you, “No, we should just keep 2,500 troops. It’s been a stable situation for the last several years. We can do that. We can continue to do that?"
BIDEN: No. No one said that to me that I can recall. (my emphasis)

Also testifying were Defense Secretary Lloyd J. Austin <