Robert: "Aboriginal" simply means the people who are native to a certain land. The "Aboriginees" of Australia are native to Australia just as the First Nations peoples are aboriginal to Canada and the USA.

No, there's a lot of controversy over where the earliest people to come to North America actually came from. The most commonly accepted belief is that people crossed from North East Russia and China across a land bridge that connected north eastern Asia and Alaska during the last ice age. But, there is evidence to suggest that North America was originally settled by people that came from what is now Spain and Portugal who crossed the Atlantic by following the edge of an ice sheet that spanned the entire Atlantic Ocean during the last ice age. It's very likely that North America was populated by different people who came from different places on the Earth, but who didn't make contact with each other for centuries after coming here. The reasoning behind that is that the people that settled in South America seem to have a form of writing which is seen carved all over their holy sites, whereas the plains Indians and Arctic peoples (starting with the Arctic culture known as the "Dorset culture", had no form of writing at all. Writing is something that a culture never loses because important events in the culture's history need to be recorded for posterity. For one group of natives to have writing and another group not to have it suggests they came to North America from different places and at different times.