What will happen if America is invaded?

"There will be a rifle behind every blade of grass."

--Admiral Isoroku Yamamoto

America has been invaded it was a sneak attack we call 9-11 the answer to that question is obvious we did retaliate with diplomacy and precision. Our Borders are constantly under attack by drug runners and illegal aliens. We respond with the same diplomacy that is an American tradition. We are a caring country as a whole. That makes it hard to really be successful with national security because of our god given rites as a human and our determination not to violate them.