To be fair, they had issued 2 announcements advising all US citizens to leave immediately. The 2nd was on Aug 12 of this year, according to this article:
https://www.cnn.com/2021/08/12/politics/us-citizens-afghanistan/index.html
The US Embassy in Kabul again urged American citizens to leave Afghanistan "immediately" amid rapid Taliban gains in the country.
It is the second such security alert in less than a week urging the immediate departure of US citizens.
"The U.S. Embassy urges U.S. citizens to leave Afghanistan immediately using available commercial flight options," the embassy said Thursday, noting that Americans who cannot afford to purchase airline tickets should contact the embassy "for information regarding a repatriation loan."
The embassy issued its alert as the Taliban continued its assault, seizing major cities and capitols, dealing blow after blow to the Afghan government, its army and the US and its allies who trained Afghan forces.