"It (nil braking action) wouldn't explain of itself the failure of spoiler deployment,..."
However, failure of spoiler deployment might explain nil (or reduced) braking action: No spoilers = more residual wing lift = less weight/force holding the wheels tight to the ground for friction.
Seems to me that thus far, what we may know, from the "proxy FDR" (the video), is that the supplementary deceleration devices - TR and maybe spoilers - did not function as expected, at least in terms of timeliness.
What we don't know is: whether that abnormal function was due to mechanical problems, including perhaps a sticky TR lever. Or crew errors in the operation of the devices. Or anything at all about the actual braking (auto? armed?, setting?, surface condition?)
Or both - I can imagine a scenario (out of many) where in the midst of a challenging approach to a challenging runway, the spoilers didn't get armed. Which might have been easily noted and corrected during the roll-out except for the distraction of recalcitrant thrust levers at the same time.
I find the bashing and defense of American to both be premature at this point - except for the fustercluck surrounding the handling of the FDR data.
