Yes, Osama Bin Laden is dead. Yes we waged war on Al Qaeda terrorists for years. But there is basically no way to end the group. There will always be people in waiting to join the group. Families are stuck in a cycle putting their children into the group. It is a way of life. So no they're not back, they never left.
U.S. operations have significantly weakened al Qaeda after 9/11. The Obama administration put pressure back on al Qaeda and took out their leader. The group is damaged, but it's still out there. It never went away.
al Qaeda will, hopefully, never be able to initiate another attack like the 9/11 attacks, but it is and has been a constant threat that our intelligence agencies need to be monitoring and fighting.