I would not generalize the poor experience in the UK with the US.
US card issuers are typically issuing temporary credits within 1-2 business days and then a permanent credit within 7-10 days so long as the chargeback is accompanied by the proper documentation which demonstrates an entitlement. The merchant acquiring banks simply are not fooling around any longer and they hold most of the cards, not the carriers.
Similarly, DOT complaints are typically acknowledged in 2-3 days and forwarded to the carrier for response shortly thereafter.
Far from toothless, the benefit is that US customers find that the DOT complaint is referred to a more senior compliance person and that expedites anything which may be left should there be a chargeback issue.
Amex, Chase, and Citi are good examples of