As an admittedly lazy follow-up to the recent discussion of empire and secession, I thought it might be helpful to introduce the papal "bulls of donation", in which the popes go well beyond mere toleration by taking an active and supportive role in the conquest of the New World. In theory, yes, there is a possibility that the involvement of the pontiffs could have been a moral or prudential error, such acts falling outside the charism of indefectibility, and good Catholics may disagree without censure. However, in the absence of any proof of wrongdoing, the faithful clearly owe Christ's Vicars the benefit of the doubt in this matter.
Contra those whose religion is Americanism rather than Christianity, no Christian can say "Americans are my only neighbors" and to hell with everyone else. Although empire building is seldom an obligation and often ill-advised, it cannot be true that the only just reason for conquest is self-defense. The example of Christian charity in the excerpt below is instructive:
From Inter Caetera by Pope Alexander VI, addressed to the kings of Castile and their successors:
Therefore all things diligently considered (especially the amplifying and enlarging of the Catholic faith, as it behooveth Catholic Princes following the examples of your noble progenitors of famous memory), whereas you are determined by the favor of Almighty God, to subdue and bring to the Catholic faith the inhabitants of the aforesaid lands and islands, we greatly commending this, your godly and laudable purpose in our Lord, and desirous to have the same brought to a due end, and the name of our Saviour to be known in those parts, do exhort you in our Lord and by the receiving of your holy baptism whereby you are bound to the Apostolic obedience, and earnestly require you by the bowels of mercy of our Lord Jesus Christ, that, when you intend for the zeal of the Catholic faith to prosecute the said expedition to reduce the people of the aforesaid lands and islands to the Christian religion, you shall spare no labors at any time, or be deterred with any perils conceiving from hope and confidence that the omnipotent God will give good success to your godly attempts.
And that being authorized by the privilege of the Apostolic grace, you may the more freely and boldly take upon you the enterprise of so great a matter, we of our own motion, and not either at your request nor at the instant petition of any other person, but of our own mere liberality and certain science, and by the fulness of Apostolic power, do give, grant, and assign to you, your heirs and successors, all the firm lands and islands found or to be found, discovered or to be discovered toward the west and south, drawing a line from the pole Arctic to the pole Antarctic (that is) from the north to the south: containing in this donation, whatsoever firm lands or islands are found or to be found toward India or toward any other part whatsoever it be, being distant from, or without the aforesaid line drawn a hundred leagues toward the west and south from any of the islands which are commonly called De Los Azores and Cabo Verde. All the islands, therefore, and firm lands, found and to be found, discovered and to be discovered, from the said line toward the west and south, such as have not actually been heretofore possest by any other Christian king or prince until the day of the nativity of our Lord Jesus Christ last passed, from the which beginneth this present year.
We, by the authority of almighty God granted unto us in Saint Peter, and by the office which we bear on the earth in the stead of Jesus Christ, do forever, by the tenure of these presents, give, grant, assign, unto you, your heirs, and successors (the kings of Castile and Leon), all those lands and islands, with their dominions, territories, cities, castles, towers, places, and villages, with all the right and jurisdictions thereunto pertaining: constituting, assigning, and deputing, you, your heirs, and successors the lords thereof, with full and free power, authority, and jurisdiction. Decreeing nevertheless by this, our donation, grant, and assignation, that from no Christian Prince which actually hath possest the aforesaid islands and firm lands unto the day of the nativity of our Lord beforesaid, their right obtained to be understood hereby to be taken away, or that it ought to be taken away.