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China has been building their fleet at the fastest rate in modern history and have the worlds largest fleet. Blue water capabilities will be within their reach by 2030.
Canada really needs to spend more on it's navy.
Longest coastline in the world. 5 diesel submarines and one is in a shopping mall. >

Why should they? Any attack on their coastline and they’ll instantly invoke Article 5 and America’s totally OP navy will come to their aid. The US would never let Canada be invaded, it’s too much of a security risk for us. >

Because America can’t be the world policeman who can simultaneously protect all of Western Europe, the arctic, North America, the Middle East, and east Asia. 
Americas Allies need to be able to stand on their own. People forget that World War Two wasn’t just America and Russia single handedly beating the axis powers. People forget that there were over 20 nations allied against the Axis. 
Can Canada take on Russia or China by itself? Absolutely not. But it should be able to hold its own so the US and NATO can help turn the tide. >

China doesn't have the ships to threaten Canada with its Navy even without the US. Their fleet can barely travel beyond 1000 miles.