It is a serious moral deficiency...

to have no greater sense of allegiance to people of one's own nation than to those of other nations:

The vice of deficiency is where fraternity comes in. Just as one can be excessively attached to one’s own family or nation, so too can one be insufficiently attached to them. This vice is exhibited by those who think it best to regard oneself as a “citizen of the world” or member of the “global community” rather than having any special allegiance to one’s own country. It is the idea of a “world without borders” and a “brotherhood of man” – hence fraternity construed as an ideal of universal brotherhood to replace family loyalty, patriotism, and other local allegiances.

To be sure, there is a sense in which all human beings are brethren; as I said above, we are all members of the human race and thus in that sense all members of the same maximally extended family. The problem comes when the idea of brotherhood is falsely taken to imply that there is something suspect about national or other group loyalties – when it is taken to imply that one’s countrymen are one’s brothers in no stronger sense than any other human being is.

The above is worth noting because of how often those lacking the virtue of patriotism try to depict those possessing it as morally suspect!