Hi @Gaz4088,
Let’s sort things out here: you can, but you don’t have to exchange your GBP into USD. The Revolut card will do the exchange for you on the fly, when you pay. It will deduct money from any of the three currencies in your account that has sufficient funds and will convert in realtime. But be aware of Revolut’s locked in rates over the weekend.
Exchanging beforehand might be a good idea if you think the exchange rate is now better than at the time you’re planning to travel. This way, you can benefit from the better rate.
Be careful if a POS terminal, or a cashier, asks you if you want to pay in “your” currency. This is more likely to happen at airports and touristy places. POS terminals recognize the card being issued in the UK and assume it is connected to a GBP account. Do not accept currency conversion here. If you then don’t have GBPs in your Revolut account, the triple conversion Macca described will happen: USD into GBP back into USD. Always pay or withdraw money at an ATM in the local currency.
Also check the FAQ section on the main website. If you are asked at an ATM if you want to deduct money from either a current account or a credit account, I believe you have to choose current account/debit card to make it work. But in a shop, it is the other way around “credit”, not “debit”.