There's more to it than that. Our freight trains are much larger, heavier, and longer than swiss/European freight trains. It's not unreasonable to think that a passenger train sharing track space with North American freight trains would need to be more heavily built, if withstanding a collision is a goal.
There are other options. Positive train control is better than strong cars - train control means the trains can't crash in the first place (they can still derail, but you can't run into a slow/stopped train in front of you as the train will automatically stop if it cannot verify there is no train on the track in front of it). This is now mandatory in the US (with a lot of fine print exceptions).
PTC generally is designed to fail safe, so it will stop the train if something might be wrong. Nothing is perfect, but everything has a compromise and strong trains have a lot of negatives - they cost more, use more energy (read global warming as it there is normally some non-clean energy in the mix).
