When traveling outside the USA you need to consider how you are going to pay for anything, from a cup of coffee to a piece of art.
Most places where travelers/tourists are welcome accept credit cards, Visa and Mastercard are the most popular. American Express and Discover may not be accepted.
Also, many credit cards charge a fee when purchasing outside the USA, so the cup of coffee for a few Euros is less expensive with cash than the credit card.
It’s always good to have some local currency with you. Whether its Euros or the West African Frank. Euros are fairly easy and quick to get from your bank or currency exchange businesses. While the American dollar is accepted in a lot of destinations, its not accepted everywhere. So check before you leave.