The United States are attacking their neighbours and allies to the north and to the south with costly tariffs on their exports. This hits especially hard because the US is by far the two nations' main trading partner.

Donald Trump has at various times offered different justifications for the punitive tariffs:

• To encourage Canada to give up its sovereignty and become the 51st state;

• To disadvantage Canadian exports and make American producers great again;

• To force Canada and especially Mexico to stop the flow of drugs at the border, particularly fentanyl.