It could also be fixed at the router by forcibly redirecting the DNS traffic to another DNS server.

Like in `iptables -t nat -I PREROUTING -p udp -s 192.168.1.100 --dport 53 -j DNAT --to 192.168.1.2`

My understanding is that if you prevent Chromecast form reaching Google's DNS servers it will allow you to provide an alternate address. Haven't had a need to try that myself, though.