Why nuclear submarines are difficult for middle powers

Does the United States oppose middle powers such as Australia or Canada operating nuclear attack submarines?

The larger obstacle is affordability and the supporting nuclear-industrial base, not a standing U.S. veto; a country must sustain people, facilities, regulation, and technology as well as buy submarines.

The decisive obstacle is usually the cost of creating and sustaining a nuclear-submarine enterprise. Britain and France can maintain their fleets because civilian nuclear industries supply skilled people, research, and facilities; Australia lacked that base, while Canada's proposed acquisition faced daunting program costs. Buying the boat is only one part of building reactors, yards, training, regulation, and institutional experience that must endure for decades.