It doesn't take much, normally it looks better to break off big chunks, (like the whole bumper, or fender), then to take it all apart, headlights and stuff can come off, but in most real car crashes, stuff crunches and bends more then breaking off. Try taking off the hood and putting it back on at an angle (a 1x1 plate would be great for this), that would help a lot and is easy to do.
Actually I think it is quite good. The vehicles could have used a little more damage, but that first picture is amazing. I'm not sure if this is the look you intended, but the semi's position is just perfect for a truck careening off a cliff and into a camp site. Great job!