iTunes should create the folder when it starts if the folder doesn't already exist. Possible reasons for it not doing so would be permissions related. Your account and system should have full access to the entire iTunes folder.
I can't test the precise behavior of the Mac version, but on Windows switching languages produces differently named folders, so that could be another way to trigger the creation. Temporarily switching the location of the preference for the media folder (not consolidating files) and then switching back again also ought to force iTunes to create the folder.
Note the Automatically Add to iTunes folder is created as a subfolder of the designated media folder under iTunes Preferences > Advanced. depending on the precise steps you've used to migrate your library this setting might not be what you think it is.
tt2