Canada–United States relations - Wikipedia en.wikipedia.org/wiki/Canada–United_States_relationsPrivate View Canada's long and complex relationship with the United States has had a significant impact on its history, economy, and culture. The two countries consider themselves among the "closest [of] allies". They share the longest border (8,891 km (5,525 mi)) between any two nations in the world, and also have significant military interoperability. Both Americans and Canadians have generally ranked each other as one of their respective "favorite nations".