I had a similar issue when the 9:45am GOT-AMS flight was actually cancelled and they moved me to the 6am, which I couldn't make. I had also applied GUCs, and the best solution for me at the time was to fly GOT-AMS the night before and overnight in AMS before my TATL to the US. The Delta agent was initially reluctant but I encouraged her to contact the AF/KLM partner desk. There wasn't any Z availability but they moved me on that short segment without any fuss (and just cautioned me I was on my own for the overnight hotel). I think the key is to get the Delta agent to connect with the partner desk, where they'll have more flexibility in fixing schedule change issues on KLM metal (and can presumably see all the KLM flights that Delta maybe cannot).