Hi Cory! I'm in Australia and my first 2 sales were to the US and Canada. I don't think there is anything to worry about as there are lots of Australian Etsy sellers who are successful. Surely the time difference hasn't kept them from being successful!
I used this site before
http://www.timeanddate.com/worldclock/meeting.htmlIt helps to check out which time is best to be online, in the forums... etc. if right times concerns you.
For me I just do it when it fits my life. On my off days I reply convos, emails or blog comments in the mornings and before bed. At about noon to 1pm I am in the forums while having lunch. Working days I only have after work hours or a few minutes during lunch.
Hope that helps!