You would be importing them to Canada when they crossed the border, and importing them to the U.S. when they crossed back. If there are duties on those goods, you would pay two iterations of customs duties on them. I am not aware of any exemption that applies.
Sometimes there are special exemptions for goods kept in temporary port side warehouses with a special legally recognized goods still in transit status, but your garage doesn't qualify.
In practice, a very large share of all goods that are subject to duties when imported to the U.S. from China are duty-free in U.S.-Canada trade due to NAFTA. But, this is dealt with on product category by product category basis, so you'd need to look at a huge phone book sized reference (does anyone know what a phonebook is anymore? do they still use paper ones like they did in the aughts when I last used one?) to determine how it affects your particular products.
There might also be special COVID-19 related emergency rules related to this international transaction depending upon the nature of the goods.