Caishen Wins

Cross-border transactions: Making a trip to the United States and notice a debit terminal at a store? You may be able to pay using Interac Debit.

Interac e-Transfers are only available in Canada for individuals who have Interac-partnered bank accounts (most of them). So, no you cannot use Interac e-Transfer in the U.S. That being said, Interac does have a collaboration with Mastercard and Western Union to allow Canadians to send International Transfers.