Hi Katie,
Welcome to Auctiva!
You can actually post auctions with USD as the currency when listing to the eBay.com(US) or eBay.ca(Canada) websites, so you still have the freedom to choose either of these sites when posting your listings even though you are committed to using USD as your currency. I suspect that your listings will be available on both of these sites regardless of which one you post your listings to, but I recommend checking with eBay's customer support team to make sure.
I know eBay is in the process of making international exposure a paid marketing tool, and I'm not quite sure how far along they are in that process. Our technical team is aware that this transition is taking place and we will be adjusting our lister page accordingly when eBay adds support for this new option to their API.
Any additional questions or concerns? Please feel free to contact our customer support team using the appropriate link on our help page:
http://www.auctiva.com/free-auction-software-help/help.aspx-Mike
