this is so handwavy about so many disciplines of human effort?

robotics? (if you can assume AGI with a perfect world model and perfect motor skills you're insanely further than we are now, like hundreds of years in the future)

military planning? (the british isles haven't been invaded since roman times, hint its not for lack of soldiers)

logistics? (power? fuel? ammunition? boats? planes? parachutes?)

law? (where are you launching your invasion from? how are you testing the killbots without being noticed? who is letting you?)

it seems like the only way you believe this is if you've given completely up on trying to understand anything and just truly to your core think that AI = magic