VPC peering does not pass external routes. We are using Transit Gateway but we need to ensure external routes are reachable from other VPCs to vMX VPC (non-AWS routes – in this case remote VPN routes learnt on vMX).
I'm not 100% sure on your question but you need to use static routing.
The VMX will need static routes added for the VPCs in Amazon, and the Amazon transit VPC will need static routes added for what exists on the Meraki side.