I have noticed that when I pass multiple regions into the CLI as below:
terraformer plan aws -r vpc --profile saml --regions=us-east-1,us-west-1

Terraformer is not able to correctly "move" onto the next region and pull it's VPCs. Instead, it attempts to refresh the VPCs it pulled from the first region (which obviously fails) and then creates a plan.json file that contains no resources. Has anyone experienced this and have a work around? If not, it may be something that can be added as a feature in the future as it appears to work just fine with the GCP provider.