* Library in Vermont and Quebec straddling the border: https://www.atlasobscura.com/articles/the-us-canada-border-r...
* Canadian train that crosses northern Maine and used to have U.S. border guards board it (can't find the resource, but I saw this on TV show some years ago)
* Thousand Islands border between Ontario and NY State, which can be easily swum in the summer and freezes over in the winter (https://www.cbp.gov/frontline/frontline-april-thousand-islan...)
* Akwesasne Mohawk reservation further east that straddles the NY/Ontario/Quebec border but tribal members do not recognize (https://www.npr.org/2017/10/28/560436303/at-u-s-canada-borde...)
* Northwest Angle attached to Manitoba, but technically part of Minnesota: https://www.minnpost.com/mnopedia/2014/02/story-behind-minne...