No.
If they obtain a visa, they are not illegal.
No, and the laws regarding marriage to an illegal immigrant become more draconian every day.
No.
no
Nothing is bad about the US, except the illegal immigrant's.
They seem to be affecting your grammar.
You can't.
Yes he has to be born in us
inside the us
Your question reveals an unconscious bias. You said,= "How can a US citizen sponsor an illegal immigrant...." = If you "sponsor" them, they are not an "illegal immigrant." Careful, the way your question is phrased says a lot about you. The very term "illegal immigrant" is insulting to ....migrant workers, especially. Mexican citizens surely don't like the phrase and, by the way, Superman was apparently an "illegal immigrant" and you SURELY wouldn't want to insult HIM.
Firstly, the person has to gain Canadian Immigration resident status, and their having been an illegal in the USA will NOT be in their favour. Secondly, the USA is under no obligation to allow entry to someone who was previously illegal in the USA, regardless of their Immigration status in Canada. Your legal or non-legal status in another country has no bearing on your immig. status in the US.
It is legal in the United States for an illegal immigrant to marry a US citizen. Once the marriage is legal, the illegal immigrant becomes a legal immigrant and can stay in the US for the course of the marriage.