Hayley, you raise a valid concern of many international Etsians.
Unfortunately many in the USA either don't know how to use the USPS web site to determine postage to another country or just don't want to bother with shipping outside of the USA.
Many feel that a buyer will convo them for rates, but they don't realize that if shipping isn't already set up to ship to those countries and the buyer is looking only at items that will ship to their own country, that those who don't have shipping set up won't even be seen.
Its really not that difficult to ship outside the USA. Sellers already need to know the weight of the package to determine the domestic postage. To determine the rate to another country, all that involves is changing the destination country to Canada and reading the rate off the table.
For shipping to all other countries, its a matter of selecting a few different countries to determine the rates. Most countries (other than Canada and Mexico) all have the same rate.
Packages that are under 4 lbs in weight can be shipped via USPS 1st class international mail. Above that they must go USPS Priority International.
The only drawback with international shipping is that there isn't any tracking available on either 1st class or Priority mail once the package leaves the USA. So if its a valuable item, the seller needs to decide whether or not to add insurance or not.
Personally, I've had more packages go astray in the USA than I've ever had for International packages.
Here's a really helpful thread from fellow Etsy seller GoTo that discusses US sellers shipping Internationally.
http://www.etsy.com/teams/7722/business-topics/discuss/6382394/page/1