It sounds like the webroot isn't properly setup in the Site Manager for the site, if it was then /public_html/ would be stripped, are you 100% sure that /public_html/ is the correct?
Connect to the server and see if the file uploaded into the correct location, if not you may need to change the remotepath and the webroot
The url will be copied to the clipboard on success and even on a failure, if it failed to upload you'll still end up with the url on the clipboard.