I only know of one break away that was posted on these boards years ago and I'm sure it's rare.
Several years ago a MH/toad was involved in a head on, ended in a ditch with the toad rear end up in the air but it remained connected, pictures posted. All 3 vehicles destroyed and the young couple in the car didn't survive.
For myself I've done everything I could to ensure that I comply with all state and Canadian laws and I'm not concerned about changing anything for border crossings. And that includes insurance as well.
John&Joey, Good points. Certainly not all of the information on towing that is posted on commercial websites is consistent. It can be difficult to determine just what are the various state requirements.