Fatigue most certainly does not equal stress. Stress is the load put on the structural members. Fatigue, in this context, is metal fatigue, or the reduction in ability to carry loads which occurs if a structural member is subjected to repeated stress above a certain threshold.
Over Va, you will overstress parts of the aircraft, most typically battery or engine mounts. That means inspection and that there is no guarantee you won't damage the aircraft. It won't break instantly though, engineering might be a precise science these days but it's still not THAT precise.
If one wing breaks off, you will have a roll moment and a loss of about half your lift. This will mean an angular acceleration around the roll axis and a downward acceleration. The downward acceleration will momentarily increase the angle of attack, and with it the aerodynamical loads, of the already highly stressed wing on the other side. Perhaps it is not all that surprising to see both wings give up together.
Fatigue, although the understanding of this phenomenon is relatively speaking rather recent, is surprisingly predictive. This means that two members, such as two wing mounts, which have been put through the same number of cycles of the same loads will be similarly weakened by metal fatigue.
I thought I was doing good trying to avoid those airport hotels... and look at me now.