While I want the USA to win, I would rather see a very close game that comes down to the last few possessions. With the silver medal at the 2012 Olympics and the World Cup championship in 2011 it's pretty much established that Japan is no fluke and in these years the best competition that could go against team USA. Any other team going against the USA would have made this a far less interesting final.
At least this isn't so mismatched that it's a game the USA has to win because they are far better. We are talking evenly matched teams that are both the best. The USA has a great defense that is unmatched and Japan is undefeated in the fast paced flurry of games in first round and has the ability to go big with any player.
The USA could find great players from other teams, as was mentioned, and plan their defense accordingly but Japan is so unpredictable as to who can come out big with anybody that the USA will be spread thin and have to be everywhere at the same time and not give an inch watching every player. I don't know if the USA can hold up but it's one more game.
Anyway, expect great defense from both teams and a low scoring game where winner wins only by one goal, not two or more.
I hope this is epic.