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.

Interac is a Debit Card network; expansion to the US is not worth the cost and effort. In the US, whenever you want to pay by credit card, they seem to need to ask Debit Visa?  Is that a debit card?  whereas in Canada, a Visa is a Visa, an MC is an MC, and Debit is done by Interac.