(Bloomberg) -- President Donald Trump's latest trade threat against Canada carries a stark reminder for businesses weighing expansion in the northern nation — tariff-free access to the US is far from guaranteed. The US imposed the tariffs because of what it described as unfair treatment of American alcohol, cars and dairy. Earlier this month, the US declined to extend its trade agreement, known as USMCA, with Canada and Mexico. Last week, Bank of Canada Governor Tiff Macklem struck an optimistic tone, saying businesses were adapting to the ongoing trade turmoil. Trump has backed away from tariff escalation before, or has carved out significant exemptions for goods shipped under the US-Mexico-Canada Agreement.