We are US citizens re-entering the USA (Dec. 25th 2021). To be clear, my son and I will not have to show proof of vaccination to cross CBX bridge (or present such at any US customs for that matter), correct? Clarification needed. Thank you.

You will need to download the app created by the Mexican Government and submit the eform for each traveler then after you'll get the clearance to cross,, no need to worry the airport staff will guide trhu the complete process. Have fun.

U.S. citizens and residents are not required to present proof of vaccination status when entering the United States. Furthermore, a COVID-19 test is not required for CBX passengers.

We just came from there 4 days ago from Tulum and we didn't need to show anything.... Family of 6

Everything is there