Pope Leo XIV’s growing popularity would tend to “reshape” U.S.–Vatican relations less by changing formal Church doctrine and more by strengthening the Vatican’s practical influence (its moral authority, communication, and collaborative channels) in ways that fit Catholic teaching on the Bishop of Rome’s primacy and mission to build unity and peace. The sources you provided show this influence working through pastoral closeness to American realities, a bridge-building diplomacy, and the historical pattern—seen under earlier “popular” papal figures—by which Catholic public devotion can amplify diplomatic and social cooperation. 1 2 3 4

1) Papal “popularity” matters insofar as it serves primacy for unity, not politics for its own sake

Catholic teaching places the Bishop of Rome’s ministry in a framework of primacy exercised for unity and, since Vatican II, in a renewed way that highlights episcopal collegiality and the Church’s ecumenical and wider outreach. In that sense, even when a Pope is widely admired, the relationship between Rome and local churches (including in the U.S.) is meant to flow through communion—supporting bishops, encouraging synodal/ecumenical approaches, and sustaining the Church’s mission. 3 5

So “popularity” reshapes relations by making the Pope’s initiatives more readily received—and therefore more effective—in areas like charity, dialogue, and peacemaking, while remaining anchored in the Church’s understanding of primacy and unity. 3 5

2) In the U.S., Leo XIV’s popularity expresses itself through visible pastoral partnership (especially with migrants and the poor)

One of the clearest pieces of evidence in your sources is Pope Leo XIV’s message to the Catholic Charities USA Network. He explicitly describes Catholic Charities agencies in the United States as “agents of hope,” serving many of the most vulnerable, especially “migrants and refugees,” and he praises their concrete works: “food, shelter, medical care, legal assistance,” and other forms of kindness. 1

He also frames migrants/refugees not only as recipients of aid but as “missionaries of hope” who can renew parish life through faith and popular devotions—turning charity work into a lived bridge between communities. 1

How this reshapes U.S.–Vatican relations (practically):

• It reinforces a climate of trust and alignment between the Holy See and major U.S. Catholic institutions, because the Pope publicly affirms their mission in terms of Church priorities. 1
• It elevates U.S. Catholic charity and migration ministry as a shared “front” of Church life—meaning the Vatican can more credibly coordinate, encourage, and recognize efforts that match its own emphasis on human dignity, hope, and closeness. 1
• It presents the U.S. not merely as a “local church” but as a place where the Pope’s pastoral vision is being enacted in highly visible ways (which tends to increase collaboration and reduce misunderstanding). 1

3) Popularity strengthens “soft power” through moral authority—an effect repeatedly observed in Catholic history

Your sources (though focused on Leo XIII, not Leo XIV) describe a historical mechanism: when papal devotion mobilizes beyond the Vatican and into wider society, the papacy can be perceived as an “immense moral power,” and Catholic public opinion becomes a basis for the papacy’s presence in politics and society even after the loss of temporal power. 4 6

That matters for U.S.–Vatican relations because modern diplomacy and influence often operate through networks of persons, institutions, and public opinion—precisely the kinds of channels where a Pope’s popularity helps the message travel further and be taken more seriously. 4

A cautious parallel to Leo XIV: while your sources do not provide direct polling or U.S. media analysis for Leo XIV, the general Catholic-historical pattern supports a reasonable inference: if Americans (Catholic and non-Catholic) perceive Pope Leo XIV as credible, close to human suffering, and effective in promoting peace and dialogue, then U.S. actors are more likely to engage constructively with Vatican initiatives. 4 1 2

4) The “bridge-building” tone of Leo XIV’s diplomacy can pull the U.S. toward cooperation on peace and dialogue

Your sources also show Pope Leo XIV consistently using a dialogue-and-encounter framework. In a message to Hindus, he calls people to “build bridges through dialogue and encounter,” joining as “one people,” and he teaches that fostering a culture of dialogue and collaboration for peace is a task for believers and non-believers, grounded in the dignity of the person and the common good. 2

This supports a diplomacy style that can reshape U.S.–Vatican relations because:

• If the Vatican’s public stance is read as constructive and peace-oriented, the U.S. government and civil society tend to have more room to coordinate on shared humanitarian concerns. 2
• Bridge-building language helps the Vatican engage multiple stakeholders (religious, civil, and governmental), which can reduce friction and increase the likelihood of cooperative humanitarian outcomes. 2

5) Nuance: Popularity does not automatically change doctrinal authority—or replace concrete policy negotiation

Catholic sources emphasize that primacy and its exercise are real, but they are oriented toward communion, collegiality, and mission—not unilateral political domination. Vatican II’s approach (as summarized in your sources) highlights the strengthened role of bishops as “vicars and ambassadors of Christ” and the importance of episcopal collegiality. 3

So even if Pope Leo XIV is more personally “popular,” formal U.S.–Vatican relations would still depend on:

• the existing channels of Vatican diplomacy and episcopal communication,
• how U.S. Catholic leadership chooses to collaborate within that ecclesial framework,
• and the specific diplomatic or humanitarian dossiers at issue.

Your Leo XIII-era scholarship also notes how Vatican influence interacted with major global issues (including mass migration to the United States) through coordination among church leadership and political realities—again implying that influence is real but not automatic. 7

Conclusion

Pope Leo XIV’s popularity would most likely reshape U.S.–Vatican relations by increasing the effectiveness and reception of the Holy See’s priorities in the United States—especially through public pastoral affirmation of American Catholic institutions working with migrants and the vulnerable, and through a consistent “dialogue and bridge-building” diplomacy for peace. At the doctrinal level, Catholic teaching grounds this in primacy for unity and mission, while history suggests that widespread papal moral authority can amplify the Vatican’s social and diplomatic reach. 1 2 3 4