While its scripted it doesn't mean you can't change the outcome of what happens. For instance near the beginning when Private Johnson or whatever goes out and gets shot, you can walk out with him and trigger the bad guys early. He won't get shot in the doorway and will still be around to fight unlike if you let him go out on his own. Also blowing up the 2nd tiger early (by grabbing an extra panzerfaust before that section instead of running back to the church) doesn't allow as many german reinforcements to arrive.