I'll be honest, I know very little about these teams. They have both pulled off some big upsets in recent times. Algeria defeated Egypt to qualify for the tournament, and they knocked The Ivory Coast out of the last African Cup of Nations. Slovenia won the two-legged playoff against a very talented Russian team to qualify.
Both teams have a few players sprinkled around the bigger leagues in Europe, though none at big clubs within those leagues. And Algeria's best attacking player is out with injury.
It all comes down to this; The most important match for both these countries is their opener against each other. If one or the other manages to get 3 points from that match, that puts extra pressure on the US and England.
For example, let's say the US and England draw, then the US beat Slovenia and England draw against Algeria. Going into the final match, the US and Algeria would each have 4 points, England 2, and Slovenia none. Depending on goal difference, a US/Algeria draw might put both countries through. I am not saying this is likely to happen, in fact I am pretty much certain it won't, but my point is that if either of these "minnows" wins the opening match, one or both of the English speaking countries in the group could be in a difficult situation.