If AR delivers you seriously late to AEP they are responsible for rebooking your travel to SLC. As MSPeconomist points out, the AR (Delta codeshare #7601) EZE-JFK may be useful to you given its late departure time.

EZE-CUN on AR, connecting to CUN-SLC on Delta, might also work.

I would be prepared to suggest AEP-SCL-LAX-SLC to an AR agent, too.

Perhaps offerings are different on your specific date of travel.