What other US Airplanes go over mach 3 ?
And what does that have to do with the false statement that drones are slow? There are quite a few that operate at MACH .5, .6, and faster. Why are you trying to spin this in another direction?
And what does the speed of the SR-71 have to do with the D-21? The X-15 was carried by the B-52, what does the speed of the mother craft have to do with the speed of the craft it carried? I guess by your reasoning the Russian "Hypersonic missiles" can't exist, as they fly many times faster than the aircraft that launch them. Or pretty much any air launched missile.
You really are just spinning in circles here. and not doing anything but that.