Commons should provide a pop-up warning before allowing you to import Commons content into all of your courses.
Currently, when you choose to import a course or resource from Commons and check the "All" box, it imports automatically into all of your courses without any option to cancel or undo. I accidentally checked the "All" box instead of the first course in the list and had no way of undoing that mistake easily. I had to spend hours deleting each piece of imported content in every one of my Canvas courses.
Until Canvas comes up with an undo option for deleting imported content, this would be a helpful warning.