I checked with my technical contact at Curt and their Class I hitch # C11311 is a confirmed fit on your 2016 Cadillac ATS 2.5L RWD with single exhaust. This light-duty hitch requires no drilling and includes the required mounting hardware. Installation instructions and a helpful article are linked for you.
If you intend to tow a small trailer the recommended towing ball mount for use with this hitch is part # 3594 and with it you can use either 1-7/8-inch ball # 19256 or 2-inch ball #... view full answer...
You are correct the only hitches available for the 2013 Cadillac ATS are 1-1/4" openings like Curt Class I hitch part # C11311 because the vehicle is not rated to carry a lot of weight so the hitches available for it are only designed to carry 200 lbs tongue weight. The use of a hitch adapter would reduce the tongue weight rating by half.
You want to make sure you are not exceeding the maximum vehicle weight capacity of the Cadillac. There is a loading information label attached the vehicle's... view full answer...
The Yakima Jetstream Crossbar System for a 2016 Cadillac ATS is composed of part # Y00425, part # Y28TR, and part # Y06123.
This setup will then allow you to use the Lockrack Adjustable Watersport Carrier part # LR54FR no problem.
I included videos of the products mentioned for you to take a look at. view full answer...