There is this really annoying condition hidden on the website as well:

A reminder that only one item of cabin baggage is permitted for all passengers flying to, from or transiting through all US airports. This item should not exceed maximum total linear dimensions (length + width + height) of 118cm (46.5") and 7kg (15lbs) in weight, and should only contain the items you need during the flight, as it will likely be physically searched. Also, please be reminded of the current restrictions on Liquids, Aerosols and Gels.

It caught me out recently in LHR, through to LAX. Check in staff manager was very rude about it. Had to check the second carry on.