The fall of Kabul into the hands of the Taliban is definitely a blow to America's credibility. There is no need to sugarcoat it. However, it is not another fall of Saigon. Biden and his predecessor Trump have wisely chosen to end the involvement in Afghanistan so that the enormous military and civilian assets can be reallocated to more strategic hotspots such as Taiwan Strait.
America has dumped $1 trillion into Afghanistan over the past two decades. It didn't produce the desired outcome. Time to cut loss and move on. Plain and simple.