Following up here with our solution in case anyone is experiencing the same issue.
Dyn thinks that this is due to: "Google Public DNS does some really weird routing, sometimes shipping requests from one POP to another for responses. If they are shipping a US-based request to a EU POP, this could explain this behavior.". Since we're blocking traffic in the EU, this could cause the weird resolution we're seeing in the US.
Per Dyn, "Google will receive a DNS query, append the originating /24 prefix. in the edns-client-subnet (ECS) data, and send that information to our nameservers. If we see that ECS information in the query, we will take advantage of it in our traffic director response."
Hope this helps someone else someday.
Jeremy