So you're willing to let many innocents lose their lives in a hopeless fight? I guess I can expect that kind of logic to come from someone who grew up in a country that never saw conflict in its own borders ever since it was created (I'm referring to the great wars). Making it an "extra challenge" isn't going to deter foreign invaders at all. If nothing else, it will make them fight harder.
How is taking away the second amendment going to make it easier for the govt to trample on other amendments like they already have on countless occasions? I should also add that hardly anyone cares about those rights but act like all is ok so long as they get to keep their guns. There's a plethora of reasons why abolishing the second amendment would actually improve conditions, but I won't get into that here. The point is, guns won't make it that much harder for foreign militaries to drop bombs on US soil. You have your guns, and they have their fighter jets, tanks, ships, helicopters, smart missiles, and so on. Thinking that the right to bear arms is seriously any sort of protection in this day and age is a childish pipe dream.