have to build the drive motor and mount, get it on the supper-duper-space shuttle - we have none that get to the moon, much less past Mars on an intercept, get to/past the asteroid on a path fast enough to allow slowing down/speeding up to intercept, then match orbits and “park” close enough to send manned suits down to the rock to mount the drive.....
All of the above makes going to the moon easy: since we can’t even get back to the moon right, even harder with today’s NASA attitudes and abilities.
Nobody was even thinking of NASA. The Treaty would be repealed, the asteroid would be claimed by a private company with the stipulation that it be removed from danger to earth and the company would mine it for whatever it is worth.
That would be precision work placing the motor on the body so that the trust is in line with the axis of rotation. Some of those bodies turn vary slowly and would require some good senors and computers to determine the axis of rotation. Still, it is doable.