You can use your US card anywhere you see the card network's logo displayed. Visa and Mastercard networks are very well supported globally, including in Spain, making these good options to look out for when you pick your travel debit card for Spain.
What is the difference between Hola Barcelona and Barcelona Card?
The Hola Barcelona Travel Card only includes unlimited use of the Barcelona public transport. The Barcelona Card Express and the Barcelona Card include unlimited use of the Barcelona public transport, free and discount entries to top attractions and more.