Not sure if this point has been brought up, but the assumption that an invading alien species would have a higher level of military technology than us is born out of anthropomorphism. We assume that at some level the intelligent life out there will act like us, and the development of most technologies throughout our history has been spurred on by competition of national armies. Our recent history shows a drift away from lethal competition, but the drive for human progression is based in the evolutionary principle that aggression means success.
Hopefully we can all get along, but if a race had the tech to come all the way to us...
Hopefully we can all get along, but if a race had the tech to come all the way to us...