"It reveals that there is no process in this administration, there is no serious policymaking process," former CIA Director John Brennan said.
"Afghanistan would be wiped off the face of the earth, it would be gone," Trump said on Monday.
The Pentagon chief defined the final goal of the conflict as political reconciliation between the warring parties rather than a military victory.
The U.S. has said it will not attend Moscow-led peace talks scheduled for Friday.
More than 80 were killed in the Islamic State attack on protesters from the mainly Shi'ite Hazara minority group.
The decision comes amid escalating Taliban-led violence in Afghanistan.
David Cameron described Afghanistan as "fantastically corrupt."
The comments are likely to make the visit of Nigeria and Afghanistan's presidents on Thursday rather awkward.
But diplomats played down the possibility that stalled Afghan peace talks might restart soon.
The brutal killing by a Kabul mob of a young woman demands action from the new Afghan president.
Afghanistan's President Ashraf Ghani said the torture described in a U.S. Senate report "violates all accepted norms of human rights in the world."
The US has given up fighting the information war -- which ISIS, the Russians and the Chinese are winning
"I'll never participate in elections in the future and won't let my family either."
The hasty U.S. troop withdrawal leaves Afghanistan vulnerable to Taliban
Kerry Faces Uphill Battle to Defuse Afghan Election Standoff After Abdullah Threatens Parallel Government
Afghanistan faces a deepening crisis over a disputed election which has stirred ethnic tensions
Ashraf Ghani's rival Abdullah Abdullah came second with 43.56 percent of the vote, the Independent Election Commission said.
The vote has been plagued by accusations of mass fraud, and refusal by either candidate to accept the outcome could plunge the country into a dangerous crisis.