One Station Unit Training (OSUT, which means new soldiers do Basic and tank crewman-specific training at the same base: Fort Benning) lasts 15 weeks, but the tank crewman-specific portion is
four weeks. Now, that will just get you a crewman who is not a danger to himself and others around a tank. Then you have to do crew training ("In the crew of this tank, I'll do this job, and you'll do that job.") That takes a while as well and is usually done at the destination unit. Then there is collective training ("How does this tank work with that tank, and incorporate infantry, artillery, engineers, attack aviation, etc.?") takes still more time. Because we are Americans, love gadgets, and has
enormous mounts of money, we do some of that in simulators, mockups of a tank interior, linked together by a computer so you can see the other tanks virtually as you maneuver across the virtual terrain. A lot of the collective training, however, is done by climbing into a tank and driving around the local training area.
Bottom line, once the crews get their hands on an Abrams, it will take weeks-months to get them fully trained. Rush that too much, and get results like the Russians have had: a lot of dead crews and burned out tanks.