That is indeed a very plausible scenario, Chipper, . . .You may think it's impossible but over half of our population is worthless and a liability. How many will stand and fight? How many are capable?
Just look at what China is doing with it's military lately. New subs, new fighter jets and new cruise missiles designed to take out large ships under radar. Wonder what's up with that??
All China and Russia needs to do is collapse our power grid, which they have been hacking into for years. Allow us to fight and destroy our own country over a year with no food and power. Do that in the late summer so we can't harvest the last crop. Let winter help with the starvation and the death toll. Then march in and take over.
But the two things most people do not understand: it would take a huge armada of ships to cross the ocean with enough troops to do any real damage, . . . they will have to bring their own food / ammo / other "stuff" to keep it going, . . . requiring another huge armada of ships.
AND, . . . as Yamamoto said some 75 or so years ago, . . . "Behind every blade of grass", . . . would be an American with a gun.
Your scenario, . . . coupled with an major EMP strike or two would seriously cripple us, . . . but there would still be some left to carry on the fight, . . . and it would be bloody, bloody, bloody.
A battle fought by us under the theme of "decimate and retreat" rather than trying to "hold the ground", . . . would very quickly wear out the supply chain, . . . as well as those being supplied. As they move forward, . . . finding the bodies of their friends and buddies littering the landscape like poisoned cockroaches, . . . they may then decide that they don't really need to do this.
And if not, . . . it will be one costly war for them in terms of body count alone. Lots of us would be there, . . . with whatever we had, . . .
May God bless,