How do region based services with a single backing database work to improve redundancy or load balancing?

I've used services where there are multiple application servers spread out throughout US, at least I have to assume because I could explicitly use urls like EastUS.email.Com or WestUS.email.Com or Euro.email.com (as opposed to just email.com. I understand having multiple application servers to spread out the load, but what I don't understand is how I can apparently use any of the above urls to access the same email address and get up to date information -- This makes it seem like all three app pools connect to the same database -- If we only have one database, how does having multiple application servers help with load balancing and/or redundancy?