Hi there, @AllenReed ...
I am sorry to see that your question was sitting out here in the Community without a response for more than two years. I think it may be because you had originally submitted this as a part of the Canvas Commons Discussion area here in the Community, but this is a question more about unpublishing items in your course than it is about using Canvas Commons.
There are two things I'd like to address as it relates to your question.
I'm importing a course I had last year. I uploaded it to the commons, to just me. And then imported from commons to the new course.
Why are you first uploading the course to Canvas Commons and then importing the content from Commons to your new course? Is that a requirement that your school has set where you are to house a copy of your course(s) in Canvas Commons? If not, it seems to me you are creating extra work for yourself. Rather than first uploading the course to Commons, you can just use the Course Import Tool to import (copy) the content from the old course to the new course. You'd want to be logged in to the new, blank course shell as you follow these instructions:
How do I copy content from another Canvas course using the Course Import tool?
But the default is to have every assignment and module published like it was at the end of the semester from the last one. Is there a way to default it to have everything unpublished so I don't have to click each assignment of page unpublished?
You may already know about this, but if you add your items to modules in your course (via the "Modules" index page), you can publish/unpublish a module and all items within it all at once. You can read more about this at: How do I publish or unpublish a module as an instr... - Instructure Community - 571 (canvaslms.com).
Again, apologies for not having a response to you for so long! Hopefully I've helped to answer your questions. Take care...be well.