I'm confused- How did the customer from France able to place the order if your ship option is USA only?
To cancel the order or ship the order is up to you to decide.
You can estimate the shipping cost from US to France with Etsy Ship tool
https://www.etsy.com/shipping/us/price-your-postageIf you ship USA only, perhaps you should remove the copy from your Shop Policies-
"Customs and import taxes
Buyers are responsible for any customs and import taxes that may apply. I'm not responsible for delays due to customs."
Hope this helps.