Yes, you can add funds instantly using a debit card in your Apple Wallet to transfer funds instantly. Apple Cash may be used at merchants that accept Apple Cash and Visa debit card. Foreign currency exchange fees will be charged by Visa. This is standard practice and covered in the Apple Cash Terms & Conditions.
E. Foreign Transactions
Once you have registered your Apple Cash Account, and as a result, your Apple Cash Balance, you may use your Apple Cash Card for transactions outside the U.S. at eligible merchant locations that accept the payment network on which your Apple Cash Card is issued (please see Section 1(F) above entitled “Registering your Apple Cash Account with Bank“ for more information on this process). If you conduct a purchase transaction in a currency other than U.S. dollars, the merchant, the payment network for the Apple Cash Card, or other association that processes that transaction may convert any related debit or credit into U.S. dollars in accordance with their then current policies. For example, the conversion rate may be either: (i) selected from a range of rates available in the currency markets (which may be different from the rate the merchant, the payment network for the Apple Cash Card, or other association involved in processing your transaction is actually charged); or (ii) a government-mandated rate. The conversion rate may be different from the rate in effect on the date of your transaction and the date it is posted to your Apple Cash Card.<<
https://applecash.greendot.com/termsconditions/