The Shahed is based on a downed US drone (Sentinel). I'm guessing the reason America can't replicate their strategy is that it's not willing to attack civilian infrastructure the way Iran is. The US does understand the threat of drones and cheap ballistics, which is why things like blackbeard and laser defenses are in the works.

If we're going to armchair QB, I think their biggest mistakes were: * Protecting some of the IRGC instead of being committed early on to either wiping out the IRGC or not. Going halfway was really dumb because it just hardened the survivors further. Killing the family of theocratic militants isn't going to make it easier to bring them to the negotiating table. * Keep saying or implying no ground invasion, this seems dumb whether you will do a ground invasion or not. * Not appearing to have a strategy of working with Iranian resistance. Even if they did a little of this, I don't see why it couldn't have been done weeks in advance of going in. Iran has a large army with a fair number of people that may defect (there were prior evidence of defections). I am not talking about IRGC obviously - I mean the conscript army which is much larger than IRGC and also has access to weapons depots. * Appearing to not realize that they would use Hormuz against you.