美国宣布暂停与加拿大的联合防务努力，这一合作机制可追溯至第二次世界大战时期。此举被视为北美安全架构的重大变化，影响两国 NORAD（北美防空司令部）等联合防务安排。

[Brief] US Suspends Joint Defense Cooperation with Canada

The United States has suspended joint defense efforts with Canada, a cooperation framework dating back to World War II. The move is seen as a significant shift in North American security architecture, affecting bilateral arrangements including NORAD (North American Aerospace Defense Command).