If tariffs evolve from a negotiating tactic to a new normal, economic and diplomatic costs to all of North America will grow.

Let's take a look at four things investors should know. A blanket tariff of 25% is now levied on nearly all goods from Canada and Mexico, with the notable exception of Canadian energy products — think oil and gas — which come with a 10% duty.

Consumer and corporate optimism have faded in recent weeks as markets began to contend with the possible consequences of Trump’s agenda.