Can I use my Credit One Platinum card outside the U.S.?

You should be able to use your Credit One Platinum card basically everywhere that takes plastic, as it is a Visa.

However, it's a chip-and-signature card and vending machines and automatic payment services for travel tickets or gas won’t work with it. Don't worry though, because you should usually be able to find a staff member to process your transaction if you’re at a gas station or buying a train ticket for example.

Please note that the Credit One Platinum charges a foreign transaction fee on any purchase that is processed outside of the United States, so you may want to get a no-foreign-transaction fee credit card instead. 

Alternatively, using a debit card can be a better option if you intend to mainly pay using your card, or take cash from ATMs. You can benefit from reduced fees or even no fees at all.