I’d actually argue that it’s practice that makes the U.S. Armed Forces so formidable. Not talking about actually being at war—though that provides immediate Darwinian education—but rather all of the practice at places like the National Training Center, Nellis Air Force Base’s Red Flag competition, and assorted games the Navy plays in places like the Tongue of the Ocean. Lots of militaries don’t practice realistically against live opponents, but the United States’ Armed Forces do. I think it’s that practice, and not so much the shiny hardware, that explains their impressive track record since the mid-1970s.
For the OP, I’m not familiar with the mechanism for the FOAB, but from the posts above, it looks like it requires dispersal of the fuel, kind of like a FAE? If so, that’s not going to work very well for use against a hard target, like the MOAB is used for (though it’d be hell on wheels against dispersed infantry). I’ve no doubt that given a sufficient incentive, the American military could come up with whatever large explosive device you wished, but I’m not sure that such a thing is really all that practical.