I'm speculating, but there's a plausible reason I can think of why there have been no US carrier turn-arounds: these carriers are subject to US law by default and the US security will probably have the passengerlist before departure. For the US to get the foreign carrier's passenger list, a whole political dance has to be performed which likely delays the delivery of the list up to a point where the carrier has already departed.
I don't think the US security is favouring the US carriers, really. Just look at what the US govt has imposed on their citizens in the name of "national security", not to mention the scare tactics to make sure their citizens don't complain too much about losing their privacy step by step.
Just my two cents.