Canada–United States relations

Canada and the United States have had a long and complex relationship that has had a significant impact on each other's history, economy, and shared culture. The two countries have long considered themselves among the "closest allies". They share the longest border (8,891 km (5,525 mi)) between any two sovereign states in the world. Both Americans and Canadians have historically ranked each other as one of their respective "favorite nations". Notwithstanding, the two countries' relations saw rapid deterioration during President Donald Trump's second term due to his 2025 tariffs and annexation threats towards Canada, with 2025 surveys suggesting increased distrust of the United States leadership by Canadians.

Since the end of World War II, the economies and supply chains of both countries have grown to be fully integrated. In 2024, every day, around 400,000 people and $2.7 billion in goods and services crossed the Canada–U.S. border. The close economic partnership has been facilitated by shared values and strong bilateral trade agreements. The North American Free Trade Agreement (NAFTA) and its successor, the United States–Mexico–Canada Agreement (USMCA), have played a pivotal role in fostering economic cooperation and integration between the two nations. Cross-border projects, such as communications, highways, bridges, and pipelines, have led to shared energy networks and transportation systems. The countries have established joint inspection agencies, share data, and have harmonized regulations on everything from food to manufactured goods. Despite these facts, recurring disputes have included trade disagreements, environmental concerns, uncertainty over oil exports, illegal immigration, terrorism threats, and illicit drug trafficking.

Military collaboration was close during World War II and continued throughout the Cold War, bilaterally through NORAD and multilaterally through NATO. However, Canada has long been reluctant to participate in U.S. military operations that are not sanctioned by the United Nations, such as the Vietnam War or the 2003 invasion of Iraq. Canadian peacekeeping is a distinguishing feature that Canadians feel sets their military foreign policy apart from the United States.

Canadian anti-Americanism has manifested itself in a variety of ways, ranging from political to cultural. Defining themselves as "not Americans" has been a recurring theme in Canadian identity. Starting with the American Revolution, when Loyalists were resettled in Nova Scotia and Quebec (in present day Canada) between 1782-83 a vocal element in Canada has warned against American dominance or annexation. The War of 1812 saw another attempt by the United States to conquer Canada, and invasions across the border in both directions, but the war ended with unchanged borders. The British stopped aiding Indigenous attacks on the United States, and the United States never again attempted to invade Canada. As Britain decided to disengage, fears of an American takeover played a role in the Canadian Confederation (1867).