Angels, according to Catholic doctrine are spirits created to carry out God's will, and as such are not of the World. The modern belief that when humans die they become Angels has no basis in scripture or Historical church lore. Pseudo-Dionysius, in the "Celestial Hierarchy", and Thomas Aquinas, in the "Summa Theologica" defined 9 choirs of Such Spirits, of which Angels were the lowest, and served as messengers. The 5th Choir is called "Principalities" and watch over the "Leaders of People", rather than over the Land itself. For patrons and protectors of Countries or Cities, you must look to the Saints, like St. Patrick is the Patron of Ireland.