These snails, an Oxychilus species, were quite common in the backyard of my sister's house in Montreal. They did not smell like garlic (yes, I did pick one up and smelled it), so I am ruling out O. alliarius. The larger one was 10 mm in diameter. I am inclined to call them O. cellarius, but they could also be O. draparnaudi.
There are no Oxychilus species native to North America. So, regardless of what species they may be their ancestors were introduced from Europe most likely within the last 200 years.
I wanted to keep 2 of them for a future dissection, but I hadn't brought any alcohol with me. So I killed them in a little bit of beer and then preserved them, until I came home, in a few milliliters of Turkish rakı, which, with an alcohol content of 45%, surpassed Absolut vodka by 5%. They now have a nice anise smell.