My own opinion on why the USA airlines are failing is that they are trying to get passengers numbers at what ever the cost.
It has always been said that any one can fill an aircraft and operate at a load factor of 100%, this is what it has resulted in.
I have watched over many years as an airline puts its fares up by say 10$, some follow and then one drops back to the original prices and low and behold within a few days it is back as it was.
How many airlines have raised their fares over the last few years, to cover the extra money that they are all having to pay out?
Just think if the airlines in the states had to operate as we have to do in the rest of the world and pay for all your costs, l think l am correct in that the US government foots most if not all the TSA costs.