gistfile1.txt

- hosts: localhost
  vars:
    result:
      vpc:
        cidr_block_association_set:
          - id: block1
            cidr_block: 192.168.122.0/24
            cidr_block_state:
              state: present
          - id: block2
            cidr_block: 192.168.123.0/24
            cidr_block_state:
              state: disabled
  tasks:
    - debug:
        msg: blocks {{ result.vpc.cidr_block_association_set | map(attribute="cidr_block") | list }}

run like this:

ANSIBLE_STDOUT_CALLBACK=debug ansible-playbook -vv vpc-test.yml

output:

MSG:

blocks ['192.168.122.0/24', '192.168.123.0/24']