The new prime minister is facing an escalating trade war with the US as well as calls for Canada to become the 51st state.

OTTAWA—Mark Carney took over Friday as Canada’s prime minister, planting a former central banker known for navigating crises in the middle of a trade war with President Trump and likely kicking off a national election.

Liberal Leader Mark Carney will officially become Canada's next prime minister within a few hours, taking the reins as the country barrels toward a general election and continues to fend off verbal and economic attacks from U.