Yes, the closure is for the land border. People fly into the US all the time. Apparently boaters need to check in to US customs either by phone or by landing at Roche Harbour.
And there is the other way....
Oh, I know you can fly in. That’s why I asked if it was different for boaters, because I didn’t know. I thought I’d mention it in the offchance you hadn’t heard about the extension and assumed the border was open.
Safe paddling!