I think pay to fly was likely on the cards in the US at one point. The industry was atrocious during the financial meltdown. Colgan, and later the retirement wave/hiring boom took care of that threat.
As you pointed out, in Europe it seems to be a long term strategic campaign against Ts & Cs. In the US, it is far more reactive (feast/famine).
Hopefully labour there is protected somewhat from the next economic wobbles, due to sheer retirement figures coming down the pipe.