North American steel and aluminum industries express concern over US President Trump's tariffs on most goods imported from Canada and Mexico, effective March 4, disrupting decades-long trade relations and intertwined cross-border industries. 

Canada immediately imposed 25% tariffs on US$30 billion worth of US goods, planning to extend to US$155 billion. Ontario vows tariffs on electricity sold to the US and considers blocking metal exports. 

Canada is considering all options, including non-tariff countermeasures, amid escalating trade tensions. The US relies on Canadian minerals and metals, including nickel, uranium, and germanium. Tariffs on metals could harm US manufacturing or force the industry to buy from other countries like Russia. 

While US steel producers seek stronger trade protections, tariffs on Canada could disrupt intertwined industries.