Is America great or Canada great?
First thing - Canada is also "America." I believe you're referring to the United States. Let's continue along those lines.
What is the US "great" at?
If you want to invade China or Russia, I'll take the US every time over Canada. They have the most powerful armed forces in the world by a significant margin. It's not even close. If you claimed they were twenty times more powerful, I'd say you're being generous. Man-for-man though, I'll take the Canadians any day.
Want to build a business? Americans have the right approach to building a business and providing top notch service. Canadians are similar but Americans are the original when it comes to this. I'll concede this point readily.
Need a heart transplant or a kidney surgery? Canada is the place for you. Canada leads the US in almost all aspects of healthcare. It's not even close. The US can only stand and admire our system (although they often mock it and criticize it to make themselves feel better, even at official levels).
Quality of life is also superlative in Canada. If you want to raise a family, Canada is the place to do it. We have great support programs, social welfare, in some cases subsidized daycare, and we have good maternity/paternity leave as well as guaranteed vacation days and strong labour laws. Our minimum wages are also far higher than in the US.
Overall I think Canada comes out the winner in this comparison, as it's difficult to see how the huge military benefits the average joe, apart from employment which is a small fraction of the budget. In any case, most soldiers are paid better in Canada than in an equivalent position in the states. It's a complicated issue, though as base pay is higher in Canada and in the US many specialties earn added pay that can overcome that difference.