Fans of The Bachelor are used to blurred-out moments on the dating show, usually caused by skimpy swimwear, but the season 28 premiere included a head-scratcher: a censored Canadian flag.

Flag makers have reported a boost in sales of the Canadian Maple Leaf. Businesses have embraced a “Buy Canada” movement and removed U.S.-made products from their shelves.

The renewed interest in Canada’s maple leaf flag, fueled by intense opposition to Mr. Trump’s idea of making Canada the 51st state and his economic threats, comes as the red and white Canadian ...