2 Answers
Yeh you can store SSL certs in IAM. This was the way to do it before ACM launched and it still an option if you have a company policy preventing the use of us-east-1. https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_server-certs.html
Also check out the CloudFront console, it clearly states that there are 2 options: ACM in us-east-1 OR IAM.