Dollars, duties and dilemmas

Material samples inside Maguire Shoes in Montreal. Ahead of the end of the de minimis exemption, Montreal-based Belzile-Maguire, co-owner of Maguire Shoes, urged customers to order from its US stores – prompting a surge in sales. — Renaud Philippe/The New York Times

THE tea farmer in Japan, the shoe company in Montreal, the chocolatier in Mexico: small businesses around the world have been roiled by constantly shifting US trade policies.

The rules have upended pricing, logistics and expansion plans as companies scramble to keep American customers happy.