President Trump’s ongoing use of Section 338 authority to impose and adjust 50% tariffs on select Canadian goods, alongside import bans effective late September 2026, stems from unresolved disputes over Canadian policies on motor vehicles, dairy supply management, and alcoholic beverages that U.S. officials describe as discriminatory. Negotiations collapsed in August after Canada rejected final U.S. demands, prompting Ottawa’s September 8 retaliatory surtaxes on roughly $20–28 billion in American exports. The most recent U.S. modifications, announced September 8, expanded covered products and added prohibitions while preserving core duties that apply regardless of USMCA origin. Trader focus centers on whether further announcements will target additional sectors or raise rates amid stalled talks and scheduled implementation dates in the coming weeks.