can i do degree in computer sci after my 12 commerce with maths in canada or USA
Yes, definitely. To take admission in a computer science degree in the Canada or USA, you don't require the combo of Physics, Chemistry and Mathematics as you need in India. So, even if you are a Commerce student, you can definitely do a degree in Computer Science in USA or Canada as long as you have completed your maths course in class XII, as CS is ultimately a very mathematics oriented field.
So, go ahead and apply for colleges without any tension. Hope I have answered your question. All the best!