Although an individual bishop does have ultimate authority in his diocese, the USCCB does have power.
Refer back to the topic of the poll. At its last public meeting, the USCCB was informed that no catechetical course used at the high school level can be relied upon. So, my answer to the poll was no. My son is in catholic high school, and by their own admission the bishops are allowing the use of materials they admit are unfit to instruct the faith. Could an individual bishop rectify this in his diocese? Yes, with the proper effort. Should he? Emphatically yes-the instruction of his flock is one of the main roles of the bishop.
To my way of thinking, this should be a priority issue, a showstopper, not allowed to continue. But I fear my son will pass through high school using bad materials. It will be years before changes are made, because it will be done through the USCCB, at their pace.
So, yes, they do have de facto power, and no, I don’t trust them to convey the teachings of the Church.