To put it simply, it's not about being big or being fast, it's about using your body correctly, it's about agility, reflexes and mental conditioning. It's the same for every sports. Otherwise Altidore or Fellaini would be world class players.
I think you missed at least part of the point of my post.
Those traits you mention, are exactly why Canadian/USA big athletic guys CAN make it with virtually no technical skills. It's because of cross sport training. We play football (the other one) and basketball. These two sports feature exactly the kind of skillset you need to excel as a donkey. We learn (and I would argue MUCH better than Europeans) how to beat a man 1 on 1 to a ball with swim moves. With basketball we learn body positioning through rebounding drills. How to aggressively OR subtly move a man marking you, completely out of position while staying in the optimal position and then to take the ball at it's highest point.
These are ball specific skill sets that are fundamental to the North American athletes formative years. These big athletes may not be able to trap a ball very well, make a long pass, or do anything technical, but they are going to make it look easy to slide past defenders on crosses, take the ball at it's highest point, anticipate and or gauge the flight path. These are exactly the reasons why out of Canada and the USA, we tend to produce an over abundance of goal keepers versus field players.
It's a niche, and they won't make it at the highest levels, but in that niche they absolutely could be effective. You take a big athletic wide receiver who washed out at the collegiate level, who played basketball and under the criteria of the OP (undroppable, play every game) they'd absolutely score some goals with their noggins.