so if I recall this correctly from my physics classes decades ago there should be an enormous amount of torque on the wing. Both engines rotate in the same direction (clockwise if seen from behind), so the resulting turning tendency is opposite to that, making the airplane roll to the left. That left turning tendency has to be trimmed out with the aileron trim, resulting in that tiny but nevertheless appreciable right wing down indication on the control wheel.
Every pilot with a multi engine rating remembers the four factors which make one engine more critical than the other in case of a failure. Three of those factors do not apply to jet aircraft, but torque certainly does, or doesn't it? And since jet engines usually are not counterrotating, there is definitely an asymetric torque situation even with all engines operating normally.
No - you are forgetting Newton's Third(?) Law, that action and reaction are equal and opposite. There is only a torque on the airframe (via the engines) if those engines exert a torque on the airflow/gasflow through them, which they do not. The exhaust stream is not rotating. Look up the back end of the engine, and you will see that the support struts for the tailcone behind the LP turbine have a slight twist, which is there to straighten the gas flow.
If you don't like that explanation, try this one. Your LP spool is rotating at, say, a steady 5000 rpm: is there a net torque on it? No - if there was, it would change speed. There is torque in the LP shaft, of course, transferring power from the turbine to the compressor & fan stages that it drives. Same with the HP spool. And, for RB211 & Trent aficionados, the IP spool, too.
The point is that all the internal torques balance out to a net zero in the design case for which those support struts are set. Off-design, there will be a very small torque. Enough to see through the described trim procedure? I don't know.
Getting the airframe rigging right involves a huge number of settings: flap segments, ailerons, spoiler panels, even leading edge slats & flaps, and there is almost endless opportunity for small tolerances to add up to a measurable out-of-trim condition. On the 737s I flew, each was different - and I suspect that some of the older airframes were a little bent, something else to consider. Remember aircraft off the same production line are not identical - every part is made to a set of defined tolerances.