It's as simple as that, if the US wins, they advance, if they don't win then they're out. 90% of you will stop reading now and that's okay, but if you want to hear the details of why they advance with a win here you go.
Currently Slovenia is the leader in the group with 4 points. The US and England have 2 each and Algeria has one point. A win would give the US 5 points and since England and Slovenia play each other both teams cannot finish with more than 5 points. If the US loses they are out, Algeria would leapfrog the US and we can't catch Slovenia with a loss.
If the US draws with Algeria, then things get a little more complicated.
If the US draws and England beats Slovenia, the US is out. England would finish with 5 points, Slovenia 4 and the US 3.
If the US draws and Slovenia beats England, then the US advances. Slovenia would finish with 7 points, US with 3, and England with 2
If the US draws and Slovenia and England draw, then it gets complicated with tie breakers. Slovenia would finish with 5 points and the US and England would have 3 a piece.
- The first tiebreaker is goal differential, with 3 ties each the US and England would have the same goal differential, 0.
- The second tiebreaker is goals scored, the US has scored 3 goals thus far, while England only has 1. This is good for the US unless England and Slovenia tie 4-4
- The third tiebreaker is points in head to head matches, since we tied England, this is a draw.
- The fourth tie breaker is goal differential in head to head matches, again, this is a draw.
- The fifth tie breaker is goals scored head to head, once again, a draw.
If the US and England are tied after all the tiebreakers, FIFA draws lots to determine who advances. Yes, you read that right, a coin flip decides the winner. If it comes down to this the US would still be the winner, as long as they know that tails never fails.