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.
This is exactly what is going to happen. More than 80% of the Tanks, Armoured personnel carriers, Multi-barrel rocket launchers and heavy artillery currently used by the Novorussian Armed forces have been seized from the Ukrainian army. Even if the Americans give them advanced weaponry, most of it is going to end up with the militia.