What if ww3 will not fought on our western soil ?

No matter where it is fought. If nukes are involved, the whole world will feel the fallout. Besides, the economy will be so fucked up that civil wars, more to militia/gangs war will spread like fire in a dry field.

hmmm. fair point.

America is the worst place in the world to try and fight a ground war if you are not America. Think about it.

100,000 enemy soldiers, one of them looks through his binocs and sees the army and marines set up and waiting on their attack. Then he looks to the left and right and sees countless tens of thousands of civilians all over the outskirts of the battle field and asks his commander "why are all these civilians here?"

The commander looks him dead in the eye and says "they're all armed...."

Everyone wants America, no one wants to try it on the ground though. Im not sure there is a way to take her without completely destroying her and the resources.

I mean, there won't be an "economy" as we know it today. Will be something along the lines of the movie "The road". Scarce food, medicine, the most basic survival needs, people acting like savages, but in reality a lot worse than in the movie. Also canibalism will not be uncommon. You know what people are capable of when starving and on the edge.

Only those that once glimpsed the whole scenario of a catastrophe like this, will have a chance to survive. A prepped mind worth a lot in such times of despair.

there will be a few token cities destroyed in the west, but yes OP, vast depopulation can be achieved by having the war in the east, you're correct.