I do not believe ATC is a valid reason. If your flight out of Dublin via CDG to the US was on a single ticket, and this led to a delayed arrival in the US, the whole itinerary is to be considered under EU261 with hence higher compensation (recent jurisprudence). Strikes are however a reason to deny claims. Yesterday (11-2) apparently a bunch of air controllers went on strike which affected ORY heavily, including my flight that ended up arriving 2-3 hours late. Even if that time window would be eligible for E261, since caused by a strike I don't even try a claim. But also in valid cases (like yours seem) airlines clearly play the 'hide and seek' game to disencourage people in the hope they give up. Not sure to which authority you can go in France if trying with AF again does not help.