This is a very cool diorama in such a small scale; however, I think it is unlikely that any terrestrial navy (US or otherwise) could take down an Imperial Star Destroyer.
With a muzzle energy of more than 300 million foot-pounds, I don't think that there would be much difficulty in getting a 16" shell to penetrate
, although the bursting charge isn't likely to do much damage, given the relative sizes, unless you got a 'golden BB' or used one of the nuclear shells the guns can fire.
The other consideration is that the maximum elevation of the 16"/50 Mark 7 is only 45°, which limits the altitude that a shell fired from the gun can reach; an intelligent Imperial commander could stand off in orbit or, if necessary, at high altitude and bombard the surface while being immune to naval gunfire.
Shipboard surface-to-air missiles would have warheads too small to have any significant effect, although if there were any AIR-2 Genie or AIM-26A Falcon missiles still in inventory, a nuclear warhead shot up the stern of the ISD might be capable of doing enough damage to the engine systems to bring one down. Be an awful long shot, though. Still, that would fit with the theme of the diorama, which only shows the end result, not how they did it.