VISA is the undisputed king when it comes to international money transactions. Its debit and credit card is accepted in virtually every country. It's this level of acceptance that makes VISA casinos extremely common on the web. Most online casinos allow players to use VISA, whether it is a prepaid gift card, credit card, or debit card.
Canada is a large country in North America with a population of just over 20 million people. Most people live close to the American border, as much of the country is too cold. Online gambling in Canada is a much more important growth sector than land-based casinos. This has been documented over the last 7 years.