Right, where you can have tie games, like NHL hockey standings use points.
They do use points for WC standings. Three points for a win, one point for a tie. In this case, though, the US and Portugal both lost to Germany, beat Ghana and tied each other. Therefore, they both had 4 points in the standings. (Germany had 7 to lead the group, and Ghana had 1 to finish 4th) The head to head result (a tie) obviously cannot be used to break the tie. The only reasonable way in this case to break the tie is goal differential.
I would personally prefer that FIFA use head to head result before goal differential, but in this case, there really is no other reasonable tiebreaker.