Here's the chart I use, which gives you the rates for international priority and first class:
http://pe.usps.com/cpim/ftp/manuals/dmm300/Notice123.pdfWhat I do for international shipping, since I generally send out my cross stitches in free frames, is specify in each listing whether the item will be framed if sent internationally (only very small frames with plastic, not glass), or not framed in order to save on shipping costs. This has meant generally that they'll be under about 4 oz, which cost me about $5.50 to the UK and $3.50 to Canada from the U.S.
My understanding is that international buyers might search by whether a seller ships internationally or not (I haven't tried this, only read it), so it is helpful to have the items in your shop that you know shipping prices for listed as available for those countries you'd be willing to ship it to. I've heard that international buyers are less likely to buy from a shop that asks for a convo for shipping -- though I myself added international rates after an international buyer requested it, and since then I've only had one other international order, so anecdotally I can't add anything to support that.
Perhaps someone else who's been open longer has a better idea of this, and more knowledge of how searches work in relation to shipping locations.