The Globe and Mail reports in its Tuesday edition that with the tariffs imposed last week, U.S. President Donald Trump has declared economic war on Canada. Guest columnist Kristen Hopewell writes that the Canadian government swiftly responded by with countertariffs on $155-billion worth of U.S. goods, but Canada's response is too limited to convince Mr. Trump to scrap his levies. We must expand the scope of our retaliation beyond traditional goods trade to target American services, intellectual property and technology -- especially those tied to the Trump-loving "tech bros" who now form part of his inner circle. We also need to work with allies to co-ordinate our retaliation and present a united front. In addition to the 25-per-cent tariff Mr. Trump imposed on Canadian goods and later partly suspended, he intends to levy a barrage of other tariffs -- on steel, aluminum, autos and lumber. The tariffs will damage the U.S. economy, but the effects on Canada will be devastating. Companies such as Alphabet, Amazon, Apple, Meta Platforms, Microsoft, Nvidia and Tesla make up 35 per cent of the S&P 500 and are the foundation of America's current global economic dominance. We could even ban or tax Facebook, Netflix and X.