This is definitely a Packer question, but you can increase verbosity of the playbook run by doing something like this:
{
"type": "ansible-local",
"playbook_dir": "/home/jyoung/git/ansible/playbooks",
"staging_directory": "/opt/jeremydemo",
"command": "ansible-playbook -vvvv",
"playbook_file": "/home/jyoung/git/ansible/playbooks/packer_centos7_stig.yml"