If the US were to be invaded by a foreign country where would the battles be set? In the city, the woods?

There wouldn't be any battles,we would just open the border and let them stream through .Kinda like what's happening right now.

Internet and power grids

any nation capable of a land invasion of the US would also need to be nuclear capable which would negate the need for a land invasion. unless it's canada or mexico. in which case it'd be on the borders pushing towards washington.

it would probably (initially) be a battle for the seaports - so id go with urban warfare

Everywhere, which is why they would be foolish to invade