加拿大和美国有极其相似的自然环境和历史背景，为什么美国能成为唯一的超级大国，而加拿大不能？

First, USA and Canada are very different. You can tell after living in North America for a long while. Just like France and Germany, they are different but Chinese may not be able to tell.

Second is about 超级大国. USA is now the only super power in the world because they spend too much on military. Smallyam is very right. Canada always wants to remain as a neutral country, though this is not the fact any more.

In terms of natural environment, come on, they are very different. Do you know Canada as the biggest oil reserve in the world? After Middle East finishes their oil in 25 years, Russia and Canada will continue to provide the world with natural gas and oil.

人少，比较寒冷。美国开发较早，主要由英国人掌握，而加拿大则由英国和法国等掌握，现在魁北克不是还要独立么？它们就是法语区。
加拿大人的生活质量并不低

加拿大从来提倡和平，人权等等的基本价值，再说有美国做它的保护伞她不必发展成为超级大国。