Hie Geoffrey,
“Clip one…Map grows from center (~.5 seconds)…breaks apart into regions which lift off screen and reveal clip two.”
I think for the separate regions lifting off the screen part to work the clip has to move with the mask path in z-space..
So you would be better off importing your clip in AE, and creating paths for different regions in which the USA map has to be broken.
Each path should be on a separated layer that will be a duplicated copy of the original footage layer and then animate those layers in Z-space to reveal the 2nd footage …
However as you mentioned that u already created masks for those regions you can copy and paste these masks on footage layers..