Typically your computer asks your firewall/router for a DNS lookup. It relays that to your ISP's DNS server. Your ISP looks up the DNS server responsible for the domain and contacts that server and sends your original request. That request doesn't include your IP however, so Akamai's DNS servers are returning regional specific servers based on your ISP's DNS server IP/geo-location. That's usually perfectly acceptable, since presumably your ISP's DNS server would be located on a good route with a low ping.
So if you replace your ISP's DNS server with those of OpenDNS, google or whatever else, it is that server which determines your location when Akamai's DNS servers decide which IPs to give you.
You should be able to replace your DNS server with your own locally hosted one as well. ie, you contact the root-servers, hunt down the responsible server, then contact it directly for the IP. I'm not sure what the implications of that is though. The intent of the typical setup is that the ISP DNS servers can cache things and reduce the load on the central root servers.