Will my bar code work in a country other than the United States?

Yes. Your bar codes will work anywhere that UPC or EAN bar codes are scanned. There are 2 formats that work together to cover the globe, the UPC & the EAN format. 

The UPC (GTIN-12) is used in the United States & Canada, while the EAN (GTIN-13) is used just about everywhere else globally. 

Between those two formats you will be able to sell internationally.