Laying It Out There

Here are the official CONCACAF Regulations regarding tiebreakers, found here on Page 19:

CONCACAF U-20 Championship Tiebreakers (if teams are tied on points):

a. Greater number of Points in matches between the tied teams.
b. Greater Goal Difference in matches between the tied teams (if more than two teams finish equal on
points).
c. Greater number of goals scored in matches among the tied teams (if more than two teams finish equal on points).
d. Greater Goal difference in all group matches.
e. Greater number of goals scored in all group matches.
f. Drawing of lots.

And here how that translates to the U.S. U-20s...

• If the U.S. wins against El Salvador... they secure advancement to the U-20 World Cup
  
• If the U.S. ties against El Salvador... they secure advancement to the U-20 World Cup
  
• If the U.S. loses to El Salvador.....
  ....AND Jamaica ties Honduras, the U.S. secures advancement to Egypt
  ....and EITHER Jamaica OR Honduras wins, they will not advance out of Group A
  

So, there it is... the US is in control of its own destiny, with a win or a draw booking a spot in Egypt.