Animated Traveling route in iMovie
Solution 1:
I don't think you can do this in iMovie but you could do it as a screen recording in Quicktime Player then import that into iMovie. Open up any paint application, open your map, select a large red paintbrush, start Quicktime Player recording then draw your route in.
Solution 2:
You cannot do exactly what you want in iMovie, but you can get close. You can put in as many GPS Coordinates as you want to make the path somewhat granular, but you probably would not want to put in all.
See my YouTube video for how to add coordinates. It is simple to string together maps in iMovie to make a path by having Map2 use the ending point of Map 1 as the starting point of Map 2 etc.
The video is for adding coordinates in iMovie 11. The new iMovie is quite similar.