So the US get 2 air strikes per air force forward observer and if they take 2 they will get a total of 4 air strikes!!
No, because you can only have 0-1 Forward Observer (either Artillery or Air).
But what happens if the plane is delayed?
Turn 1: call in air strike
start of turn 2 roll to see what happens and the plane is delayed, so I re-target the first air strike.
Turn 2: Can I now call in a new air strike against a new target so have 2 markers on the table?
The first airstrike has to be completed before you can call in another one. If the first one is delayed, its delayed. You cannot call in a second one.