I agree. If I'm doing my math right, today's game doesn't really matter for the US when it comes to advancing out of the group.
Even if we lose, we still control our own destiny. A win against Iran and we go through, but a draw doesn't help us.
If we defeat England, then we still need a win OR a draw against Iran.
If we draw today, we still advance with a win OR a draw (based on GD) against Iran.
This is all assuming Wales draws or loses to England. If Wales defeats England, it will get messy.
So, we may as well go all out and win.