From a process standpoint, calling back to Delta in the USA frustrated the resolution. Most DL agents in North America no longer have the insight into AFKL PNRs necessary to deal with complicated interline issues. Had you called Delta in Europe, however, you would have reached AFKL agents with Deltamatic access who would've identified the problem sooner and likely just reissued your itinerary onto KLM 074 ticket stock to keep you moving along.