Take a current snapshot photo of the internet. Most of the computers and most of the internet users are in North America, particularly the USA. The numbers in Asia and Europe are growing significantly, but keep in mind at the time of this writing that the US accounts for the majority of internet traffic. South America and Africa are not even a blip on the Radar Screen.
Lets look at economics. The GDP per capita of the USA (1998 estimate $31,500) is at a level where its citizens have more disposable income than anywhere else in the world. This is important too, as disposable income is directly proportional to money spent on gambling!
As an example, Sweden has a high disposable income as well (1998 estimate GDP per capita = $19,700) , but compare the population of Sweden (8.8 million) versus the USA (270+ million). As you can see, the USA is "where its at" for online gambling for the immediate future. Long term they will probably account for about 15-20% of all internet gambling, but for now, the USA continues to represent an extremely high percentage of internet gamblers.
Obviously, this is a serious consideration in any overall business model when it comes to online casino revenue. However, recent policy decisiond by issuing banks that use Visa and Mastercard have negatively affected North American Gaming revenues. As such, Europe has now become the "new frontier" for internet gaming.
Most Online Gambling Software Providers have software that recognize the Internet Protocal (IP) address. The IP address is like a phone number. It tells other computers exactly where you are in the world.
The Internet Casino Software would be programmed to block out IP addresses based in the USA/Canada. In addition, the software would not accept any credit card with a USA/Canadian billing or mailing address.
Most online casinos offer "Play for Fun" to customers blocked from gambling. For those individuals, the game would operate similar to casino software bought in a computer store.