Culture, yes, but there are legal differences which limit cross-border investment flows more than cross-border cultural or more-transactional-commerce flows.
At the federal level, Canada generally flip flops between Tories and Liberals every so often and the US generally flip flops between Republicans and Democrats every so often. After 8 years of Obama, the US was due for a flip. After 10 years of Harper, Canada was due for a flip.
Not to mention that most of Canada's population - Greater Vancouver and the Windsor-Quèbec corridor - border the most left leaning regions of the US excluding California; the Pacific Northwest and the Northeastern US respectively. Alberta politics are roughly similar to those of Montana or the Dakotas.
