The War of 1812 is one of the most controversial wars in United States history - at least for those who pay attention to history. From the Canadian perspective, the War of 1812 represented Yankee greed and expansionism. Come to think of it - that's pretty much what most critics of the United States believe, including - of course - historians like Howard Zinn. In this view, the United States got greedy (a common theme of anti-American criticism) and tried to take Canada. The Americans were (according to this refrain) turned back and the War of 1812 ended in a stalemate (generously agreed to by Britain, notwithstanding that embarrassing, post-war loss at New Orleans).
Well...there's a little more to the War of 1812 than that. While westward expansionism played a significant part in American motives, the United States was NOT the aggressor nation.
For more on the causes of the War of 1812, check out this article over at Suite101.