Hmm,
There were 8 groups, each with 4 teams. The 2 top teams in each group go through to the next round. The USA came second in their group (D) so they play the top team in Group G, which was Mexico.
This is a straight knock-out from now onwards, the winner of the Mexico v US match will go on to meet Germany, who won their match today against Paraguay.
If, after 90 minutes play, the result is a draw, then play will continue until a goal is scored. This is known as The Golden Goal. If, after 30 minutes play, no winning goal has yet been scored, the match will be decided on penalty kicks.
Oh, and yes, the soccer fan was indeed pulling your leg about the 5 goals.
Englishman.