Drivers are sometimes amazed at the level of damage that cabs sustain in relatively minor rollover accidents. They seem to think the cabs should be stronger, like the truck ads suggest they are. But what the manufacturers produce is not strong cabs but (at best) durable cabs.
Durability and strength are two different things from an engineering perspective. Consider how cabs are tested. American manufacturers do the "bump and shake" tests exclusively. Cabs are put in testing fixtures and bumped and shaken in a lab or driven over special testing surfaces that are suppose to replicate real world operating conditions. The idea is to make sure that the cab doesn't fall apart too quickly on the road.
But these are tests of joining technology, or assembly procedures; they prove nothing about the absolute strength of the cab itself. Very light components, if fastened together well, will do just fine in these tests. And that's what your riding in; a cab which is light and durable but not strong. The welds are good, the rivets and huckbolts are good, good enough for the eggshell components they're suppose to hold together; but the components themselves are designed to be light, not strong. That's why trucking is the most dangerous major occupation in the country.
Until very recently, no American manufacturer had ever done a rollover test on a heavy truck. A few cabs had been tested against the EEC or Swedish standards and they generally failed. You can't sell most American trucks in Europe or Great Britain; the cabs are too flimsy.