I would argue that the diocese is the local Church, and what the Ordinary says is what the people must follow. The USCCB, likewise, adapts the doctrines and practices to the local Churches.
The USCCB has loosed the requirement for meat abstinence outside of Lent. That’s all they had the competence to do. They have no authority to loose the requirement for penance, since it is Divine Law.
True, but Divine Law does not specify Friday. The Church in the past has said that we will all do penance on the same day. However, Canons 1249 to 1253 are talking about abstinence as the penitential act. I’m confused, slightly. The USCCB says that is no longer true we have to abstain under penalty of sin. It is now voluntary to do penance on Friday.