A person who regards the whole world as his country

One word substitute is Cosmopolitan.

Patriot: a person who vigorously supports their country and is prepared to defend it against enemies or detractors.
Nationalist: a person who strongly identifies with their own nation and vigorously supports its interests, especially to the exclusion or detriment of the interests of other nations.
Cosmopolitan: familiar with and at ease in many different countries and cultures.
Metropolitan: relating to or denoting a metropolis or large city.