A little history might explain why US training of other militaries doesn't work. During the Normandy invasion in WWII, the Germans were solid fighters but were overwhelmed by the sheer amount of material the Allied forces were plowing into the continent. A "will to fight" is meaningless when bombs and artillery shells are raining down and tearing apart man and machine (especially, in that case, with no effective air opposition from the Luftwaffe, giving the Allies air superiority).

The US has a history of arming others that they want to support, but "training" may be limited to how to use the gear (including coordination of forces). If it doesn't also include (and may not be possible to include) a solid will to fight, then you get what we see today -- US-backed fighters dropping their US-supplied gear and running away, and the enemy gaining the use of all that equipment.

The answer might seem to be US taxpayers demanding that their earnings not go toward this de-facto arming of "enemy" forces. That ignores too much, however, including decades of accumulation of effects, electoral politics, cultural myopia, and more. I can't offer a better answer, but I don't see this "answer" happening anytime soon -- or ever.