Can the API name of a field be edited?
If yes, GREAT! How?
If no, is the alternative to delete field and create new field? If this is the case, what if this field is used in a multitude of times across different smart capaigns? The only way I can think of accomplishing this is to create the new field with the correct API name and then manually go into every scenario where it is being used. Re-create the criteria (Smart List/Flow steps) that uses this field, then delete the step that uses the old field. I hope this is not the case.