Expanding the geographic range for Waymo is straightforward: do the same thing in a new place (plus new hurdles like snow, but that isn't currently the limitation to growth).
It isn't clear how Tesla goes from "FSD" to "full automation". They are working on the "draw the rest of the owl" step.
I'd say the opposite. It is clear how Tesla goes from where they are to "full automation" – they just improve their models. Easier said than done, sure, but there is no conceptual leap required.
Meanwhile, for Waymo to jump from level 4 to level 5 requires handling edge cases which it is actually not clear can be handled by the system Waymo has built. In huge swathes of the world, weather conditions are not conducive a system that relies heavily on LIDAR / roads change too much to be effectively mapped like they've done in very stable metropolitan areas like Phoenix and SF / etc.
Said another way: our existing roads are built for entirely visual agents (humans). Getting a system that heavily relies on non-visual sensing (e.g. LIDAR/Radar) to work well on a specific subset of those roads is clearly doable, but that doesn't mean it can be generalized to our entire automobile infrastructure.
At some point "doing the same thing in a new place" is not going to be economically possible, unless the company is somehow able to continue getting money to burn (or unless they get much much better at bringing new places online).
It isn't clear how Tesla goes from "FSD" to "full automation". They are working on the "draw the rest of the owl" step.