The TSA itself said there were no actual active threats in the years following 9/11. However if there were the TSA wouldn’t likely be able to stop them since they miss most of the contraband going through checkpoints.
Nonetheless because of our fears – even our imagined ones – we’ve given up our freedom to travel. We have to carry papers with us and show them to authorities on demand. We go through invasive screening. And it’s all become so normal we don’t even question it.