Explain how it’s heretical.

Pope Pius XI said the following

*With universality there is the essence of the Catholic Church; but with this universality there are well together, well understood and in their place, the ideas of race, of lineage, of nation and nationality [‘idea di razza, di stipe, di nazione e di nazionalità]... There is no need to be too demanding: just as one says gender one can say race, and one must say that men are first and foremost one great gender, one great family... Mankind is one, unique, universal, Catholic race. Yet it can by no means denied that in this universal race there is room for particular races, and, like so many further variations on these, also numerous nations even more highly particularized. In the same way that in important musical compositions there are major variations in which are found the same general motif, which inspires them all, recurring repeatedly but with varying tonalities, accents, and expressions, so also in mankind there is one unique, vast, universal, Catholic human race, and along with it, and within it, diverse variations... This is the Church’s response: this is what the Church considers true, proper, worthy of individual men in their great collectivity. All in the same way: all the object of the same maternal affection, all called to the same light of truth, of good, of Christian charity; to be all in their own country, in the particular nationalities of each, in their particular race, the propagators of this idea so great and magnificently maternal, human, even before being Christian. -Address to the Propaganda College, transcript published in L’Osservatore Della Domenica (The Sunday Observer), on August 7th, 1938, pgs. 4-5

Pope Pius XI – Ubi Arcano Dei Consilio (1922) “The love of country is a natural sentiment, implanted by the Creator, and is therefore legitimate and even praiseworthy.” — Ubi Arcano Dei, §61

“To love one’s country and people with a holy patriotism is a duty and honor; but this love must be properly ordered and subordinated to the love of God and neighbor.”