@Ichabod:
Simon, I�m speaking from actual game experience having played a game against Gen Cre who gave Iraq to the US on turn 4. He�s a great allies player and is one of the contributors to BM3.
You don�t drive across north Africa that takes an extra turn longer. Look at the map please.
West Africa turn 1 (land a tank or a mech)
French Equatorial Africa turn 2
Egypt turn 3
Iraq turn 4
Bombers or regular planes catch up. In our game Gen Cre took the risk of strafing Iraq by the UK to soften it up; whch entails other risks but it worked out perfect for hin cause there was only 1 infantry remaing.
If you are gonna get US units fast to the middle east this is the way to go, shuttle fast movers (and inf) to french west africa, then you can have the US armor get to Iraq US4. Build factroy USA 5 and deploy first units USA 6. The problem is that in most cases Germany can start driving south on G7 or G8 making the factory very vulnerable. But it is possible if you have a plan and that plan must involve stopping germany from going south.
I think the biggest merits for USA troups in the middle east is to can open for the british. Sometimes the british get a good size stack that may treaten Germany or Italy stack, but if USA can can open,it is sometimes enough to discourage Germany to go south, but it also allowes the british to land planes there on the newly captured USA areas, making a Germany counter hopefully impossible