My tooth broke completely out and only has a small stub of tooth left, can a crown still be put on?

Unfortunately, based on your description it may be hard to salvage a root canalled tooth that is almost broken to the gum line. Your best alternative might be to remove the root tip and consider a bridge or implant supported crown. Of course, without xrays or photos, you should see your dentist as soon as you can. Good luck to you.

Hi:
Unfortunately without photo and X-ray it is difficult to give you accurate advice.  Please post photo and X-ray of the affected area.  Generally, if the tooth is still restorable, a post, build up and a crown can be placed.
Best,
Dr. Maddahi

Whether or not the tooth can be saved depends on how much healthy tooth structure is remaining and I can't tell you that without seeing a photo and/or an x-ray of the tooth. You should see a dentist as soon as possible.