Issue to your claim is determing what happened and why to your ticket. The flight is covered even though not ex-EU as you bought as part of one fare. The main issue there is that all the flights were sold as same carrier. Ie SEA-LAS was sold as AF/KL/DL and so were the EU flights. If it was marketed different the airline can make a case it doesn't.

You need to ask AF (not KLM) why you were removed from the original SEA-LAS as it operated as scheduled. AF or DL (depending if they operated CDG-SEA) could either be responsible for paying. If AF operated CDG-SEA then 100% is AF responsibility.

This sadly is not IDB under US DOT rules unless flight went out full and you had a valid ticket.

last question. Did CDG-SEA have any delay posted, that was then shortened?