I’d suggest starting from the premise that American/Canadian football is nothing like soccer, hockey, basketball, or any other sport that involves continuous, fluid movement, with on-the-fly decisions and actions. Rather, it is like a chess match.
One play, and the other team’s response, affects the next play and the other team’s response, and so on and so on. Like chess, sometimes the move takes a little while to figure out, which is why play stoppages happen, though within a prescribed time limit before the game goes again. As such, the game doesn’t “flow,” like soccer, hockey, or basketball. It starts and stops, as it was designed to do. Also, like chess, it’s a game of strategy: “If we do this, and they respond that way, as we expect, we should be good. But what if they don’t? Can we salvage this somehow if they X, Y, and Z?” This is a game that requires brains as well as brawn.
The chess analogy is a good one, I have found, when dealing with friends from the UK and Europe, who try to equate soccer/hockey/basketball to American/Canadian football, because they’re used to sports where the action never stops (well, it does, but not as often as in football). But the chess analogy helps a lot: move, respond, assess field position, make a decision; move, respond, assess field position again, make a decision, and so on.
Once that’s understood, the rest should be easy: get the ball into the opponent’s end zone to score. Details as to how that is achieved can come later, but I have found that the chess analogy works well to explain to non-North Americans why our football is nothing like soccer or other free-flowing sports. Once they understand that, the details–scoring, player positions, player functions, etc.–can follow.