I was trying to do that a couple of days ago. I didn’t really get the hang of the Beier Mask to work so, what I did was to take a map of the U.S. off of the internet, save it, then took the same picture to PhotoShop and drew a line from point A to point B, and saved it under a different name. Put the map without a line on the track, then take the map with a line and place it on the same track next to the first one. Now, overlap the two pictures a little till you see the crossfade. Now select transitions, and select the Linear Wipe transition. Now depending which direction you are going, determines which linear wipe you select. ( traveling east to west, select the “right to left hard edge” wipe ect.) Drag the transition into the crossfade area, and you have it.