Gray market imports into the US from China have already been big business, especially among counterfeiters and drop-shippers. Idk about getting a full-sized SUV over the border. But designer bags, electronics, and the like have been coming over for at least a decade.

Idk how much retail buyers save, though. Much like with the drug trade and human trafficking, there's inevitably an enormous mark-up for this kind of smuggling. And because it is functionally unregulated, you get a ton of refurbished, low-grade, and outright fraudulent sales. Smuggling tends to accrue money to the smugglers and the various officials you need to bribe to move the merchandise. You rarely see retail level discounts, unless the market is so glutted with knock-offs.

Canada–China trade war

Might be worth doing a little research. Canada's never been shy about using them.