Having just returned from the States, travelling with AA, I was appalled at the size and weight of some of the pieces of luggage which were being stowed in the overhead lockers, both on the international and internal flights on which I travelled.
Your laptop and briefcase would pale into insignficance, when compared with what were virtually full sized suitcases and bags (multiple) which were carried into the cabin. In most airports, there were the empty metal cradles to show how much volume should be taken up by luggage (a good idea), but they might as well have not been there!