Yes, according to Calvinism. It is sufficient. It's not effective and neither is it in your system. It's not effective to those that die in unbelief. Read the Cannons of dort, it specifically states that the atonement was sufficient of all.
How can it be sufficient? It has no effect on the unelect. Sufficient for what?
I don't need to read the Cannons of Dort. Why do I care what it says? Is it inspired?