All this would make it legal without war
Political Will: Both countries would need strong political will from their governments and public support. Leaders in both the US and Canada would have to advocate for such a union.
Referendums: Both countries would likely need to hold referendums. Citizens of Canada and the United States would vote on whether they support the union.
Bilateral Agreements: Canada and the United States would need to negotiate and sign a series of bilateral agreements. These agreements would cover legal, economic, social, and political integration aspects.
Legislation: Both the US Congress and the Canadian Parliament would need to pass comprehensive legislation to facilitate the integration. This could include amendments to the US Constitution.
International Treaties: International treaties would need to be revised or created, covering aspects like trade, defense, and international relations.
Economic Integration: Integration of economies, including currency alignment, trade policies, and regulatory standards, would need to be addressed. This would be a complex and lengthy process.
Cultural and Social Integration: Programs to promote cultural and social integration would need to be established to ensure smooth assimilation of Canadian citizens into American society and vice versa.
Transition Period: A transition period would be necessary to gradually implement all changes, potentially spanning several years.