Interesting match-up. The 2 teams met 4 years ago in the finals of the last World Cup. The 2 teams were tied 1-1 at the end of regulation. (US up 1-0, then Japan tied it.) They then were tied 2-2 at the end of extra time (again, US up by a goal, but Japan scored with 3 minutes remaining off of a corner). As such, it went to PKs to determine the winner, and Japan won 3-1 in the PKs.
The US had quite a few scoring opportunities in the 2011 World Cup final. They were just off frame, or Japanese goalie Kaihori made a nice save. I recall worrying that all the missed opportunities would come back to haunt the US, and in the end they did.
The Japanese employ a very intricate passing attack. No other team has such a precise system.
The Japanese have yet to lose in this year's World Cup. The only game they appeared vulnerable in was the semifinal, when the British approach was to use high pressure (forwards don't sit back, but attack the defenders before they can get comfortable and pick where to pass). The US switched used high pressure in their quarter and semi games (against China and Germany), and looked to be a better team when they employed that tactic than they had in their previous games, so I would expect to see high pressure from the US. To counter that, Japan is probably going to swing the ball around the back quickly, and try to your their passing system up the sidelines.
It should be an excellent game. If the US played as they did in their past two games, then they should win, but soccer can be a funny sport, especially at the elite levels.