I have never seen the invaders take too long on this strategy.
It takes 2 turns, 3 at the most to have the red and blue invaders touch. Then they go north. How are you stopping this from occurring? Given all red forces are involved in making this happen, we find it very difficult to even slow down the Red forces.
The US must continually defend the DC area because at any time the Red forces can put new troops at that location and take DC if the US is not careful. This will open up the north east which the US cannot allow under any circumstances so he must always leave forces there. Given the new card that allows the invader to attack first, it is now required that the US leave twice the usual forces in the north east as compared to the old game.
All the invader's bombers are placed on the board the first and second turns to get the maximum usage from them. They almost guarantee that any early pockets of US resistance are crushed in the 3 corresponding sectors. Once the bombers are gone around turn 5 the invaders are well established. This used to be a big help to the US as the invaders had a difficult time getting men to the front lines later in the battle. With the new movement rules of the mobile units, this is no longer a problem. Once the bombers are gone the mobile units can easily get the men into position to create combined arms which definitely makes up for not having bombers later in the game.
The US bombers do not last long in any game as they are the first thing that is targeted in every battle involving air units.
The yellow forces funnel all their troops through the south west which makes any resistance in that sector next to impossible. By the 4rd turn the western invader is always destroying Colorado springs.
Meanwhile, the invader should always harass the US by having men or mobile units take open territory upto 2 to 3 spaces away from the main attack vectors I have described.
If the US can lure the blue forces to travel directly north or north west then we can use him to block the yellow advance. This works occasionally with inexperienced players. However now that we know this trick the blue player only travels north once he touches the red and only parrellel to the red.
Under the current game rules this always works for us. What strategies are you using to allow the US player to survive? Under the strategy I outlined I have never seen the invaders take more than 3 turns to take Atlanta and begin marching north. If you could please explain your strategies, I will try those the next game to see if we can lengthen the US survival time.