Missile Defense = Maginot Line (21st century)

Can I ask why you are comparing WWI to today's War's and Soldiers? Walls, bunkers and ditches made for protection have been around for Centuries... i.e. The Great Wall of China.

And something you didn't seem to actually say or decided to miss. WWII we were invaded... via Planes and Boats. Hawaii (at the time a territory) is obvious enough. But Alaska (also a territory at that time) was also invaded. Quite a few islands were taken over via the Japenese and in some cases the Japanese soldiers were also left to die there, when our Navy arrived.

I guess I am not understanding your reference.

You negelect to mention that many of the French were sympathetic to the Nazi's, hence the very weak resistance in the first place.

By the way, missle defense is used to shoot down missles shot at us. How does the Coast Guard protect us from missles? Throw a lifesaver into the air when they see one coming and hope it gets caught in the center and they can pull it down from the sky?

The French put too much effort into constructing the Maginot Line. Had they put that effort into creating armoured divisions instead, they would not have been run over by the Germans so easily in May of 1940.

The USA in the 21st Century needs to protect itself from an enemy who wants to put a 200-400 pound nuclear device into an American city.
There are many ways to do this. The least likely, in my opinion, is ontop of an ICBM, Cold War style.

If a 15 year Mexican boy can sneak from Tiajuana to Los Angeles in a day, why wouldn't the enemy just smuggle in a nuke bomb?

How about putting a nuke bomb on a private business jet (or several jets simultaneously) and fly into an American city. How many corporate or private jets fly into US air space every day?

I just don't think the enemy will attack us in a familiar pattern.

Many French were sympathetic, but they put up a fight, until the Germans broke through in the Ardennes. The British had about 200,000 troops on the continent also.

I mentioned the Coast Guard because it seems probable that an enemy might sail a boat across the Atlantic into an American city's harbor with a nuke bomb. Is every boat that enters US territorial waters challenged by the US Coast Guard or US Navy? I've heard no.

The French suffered 212,000 military deaths and 267,000 civilian deaths. More than the US combined.