The bridge to Campobello Island is from Maine to Canada. The island is Canadian while the access is via Lubec, Maine. So you need a passport. Yup. They don’t much check going into Canada. But the Americans are a pain. They stop you and ask whether you are a smuggler. Of course the reason you go is to see the Roosevelt house. FDR summered there. And there is a nice lighthouse.
Now I would not mention smuggling except that my former office manager, no name please, was with me once. We traveled over and stopped by to pick up a six pack of Canadian beer. Coming into the US a very nice border guard asked if we had anything to declare. She quickly answered no. I glanced back at the six pack sticking up from my jacket making a rather obvious bulge from the back seat. As we departed the gate, she turned to me and said, “I’d have drunk that six pack right there rather then pay any duty.” Oh, the life of an amateur smuggler….