I reviewed the suggestions sent previously, and I could not solve the problem. The problem is that the "country" field (country_id) disappeared from sight. And I added the field "Pais2" that created a column in the database other than "country". The problem is that the "country" field is not in invisible mode within odoo studio. And, I'm not allowed to delete the "Pais2" field that I created. In this link is the HTML code of the view.
https://drive.google.com/open?id=1xwz0YyCi7CcD_rOdbY9mt1wZRCBbGkAW
This should be a hint to the benefit of using meaningful and concise question titles...