I used to limit my sales to the CONUS but a friend convinced me that I would have better results if I went worldwide. This paid off on a bicycle that I had listed at a high price. I had over 80 people watching and got one bid seconds before it ended. That bid was from the UK.
I am not a steady ebay seller. I just sell stuff that is extra or that I have lost interest in. I finally broke down and bought a couple of scales to figure shipping charges accurately and that made selling overseas easier. Selling out of the USA requires a bit more work in that I have to go to the PO and do the customs forms but it has been worth the extra time.