That seems like an unintentional straw man. The actual counterfactual is: "had I not pushed the ball, it would not have rolled down this hill [at the moment it

That seems like an unintentional straw man. The actual counterfactual is: "had I not pushed the ball, it would not have rolled down this hill [at the moment it did]". That says nothing about whether some other cause could not push the ball over at a later instant. Equivalently (if you don't like separating out the causes in time), if formulated as an OR operation on a bunch of causes, the counter factual would be: "Had I not pushed the ball, either the ball would not have rolled down the hill, or there would have been another cause for pushing it down the hill."