A few factors:
Russia has lots of factories in Europe so it make sense for Russia to focus on Europe where the battle requires large stacks.
One map has Russia being neutral to Japan, so that it can focus on Europe. That means USA should go after Japan alone.
If Hawaii and Alaska are 3PU, then it is worth it to build factory there. Hawaii halves the distance to major battlefields. Alaska troops can reach Russia far east better than Russians can. Unless you are talking about trains so that Russia can fight on 2 fronts.
3)U boat factor
Regardless of which version rules you use, if you do not cross the Atlantic you do not need a large navy. Either bomb the u boats from the air or just ignore them.
The only time u boats are scary is in one map they can sail over Canada through the Arctic. Its a WW1 map where the German has a navy squad in the Pacific.