KLM issues 074 tickets, if you really have a 075 ticket that would be Iberia. If you booked Iberia flights that were rebooked onto KLM then most likely you indeed should not be receiving mileage credit with Delta.

If however you booked a KLM flight normally (No irrops and having KL flight numbers) then you should be able to earn with Skymiles according to the regular rules:
https://www.delta.com/us/en/skymiles...rline-partners

Every paid business class fare is listed there. You may want to double check as I would expect that AMS-MEX flight to allow earning miles.