Mmm, yeah. About that. I live on Guam, which is amazingly close to Australia, and I still get pings of 400+ to Aussies. To Americans, I get about 200 ping, and to other Guam players, very close to 0 because the island is so damn small. So yeah, playing with Americans will pose a problem for you.
From what I've seen though, Demigod is substantially less laggy than other games, but then I'm not an Aussie.