Bishops like Joseph Strickland of Tyler broke cover, calling the Vigano allegations – which came with a call for the pope to resign – "credible" and demanding action.
As the bishops waited for the pope's own reforms, which came the following year in the form of Vos estis lux mundi, and for the McCarrick report, which is still on the papal desk, patience wore obviously thin.
Yet many of the same bishops supposedly implacably opposed to Pope Francis have now returned from Rome singing his praises.
After meeting with the pope in January, Strickland announced that "Pope Francis was great." He also walked back his support for Vigano, saying he "never intended" to embrace the former nuncio's call for the pope to resign.
"[It] makes you realize that it's always a bigger picture than maybe the slice you are looking at," Strickland said after sitting with Francis in January. "I certainly am not ready to judge the actions in the moment of any of the pontiffs."
Francis was more than typically generous with his time, as the American bishops took turns filing through Rome, offering them two hours or more at a time to sit and discuss their priorities and concerns. That generosity has shown results.
Bishop Robert Baker of Birmingham called the pope's session with his regional group "very open-ended and positive."
It "was a beautiful meeting," he said.
Archbishop Timothy Broglio of the Military Archdiocese said the pope "was very open to our commentary and he basically left the themes we would treat, he left that to us, what we would introduce, what we would ask."
"He was very friendly. We talked about all sorts of things, from the formation of priests to preaching the Gospel in today's world, to also working together as an episcopal conference."
Beyond addressing the bishops' desire for the McCarrick report, the pope showed a willingness to speak to distinctly American concerns, and even the internal politics of the USCCB, in which some bishops have portrayed themselves as interpreters of the pope among their brothers.
During the last USCCB meeting in November, temperatures rose during a debate about the "preeminence" of abortion as an issue in American public life.
A barbed floor intervention from Bishop Robert McElroy appeared to suggest that bishops who think that abortion ought be the preeminent social concern are out of step both with Pope Francis and Church teaching.
Archbishop Chaput responded, to applause from the other bishops, saying "I am against anyone saying that our stating that [abortion] is preeminent is contrary to the teaching of the pope, because that isn't true. It sets up an artificial battle between the bishops' conference of the United States and the Holy Father, which isn't true."
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Archbishop Joseph Naumann, who chairs the conference's pro-life committee, discussed the matter with Francis directly during his own ad limina in January.
According to Naumann, Francis encouraged "identifying the protection of the unborn as a preeminent priority."
"His response to that was, 'Of course, it is. It's the most fundamental right,'" Naumann said at the time.
Another hot-button subject Francis willingly discussed with American bishops was the LGBT-themed ministry of Jesuit priest Fr. James Martin, which has divided opinion across US dioceses.
According to several bishops, Francis made clear during one ad limina session that his reception of Martin in a much-tweeted meeting last year was not an implied endorsement of the priest's work, and that the pope was not at all impressed with the way the meeting had been used to frame Martin's public profile.
While confirming the pope's expression of frustration about the meeting's framing, Archbishop John Wester disputed reports from some bishops that the pope said Martin and his superiors had been contacted about the affair, while affirming that his recollection that there was indeed mention of ecclesiastical leaders needing to clarify some aspects of Martin's ministry. Wester also challenged a description of the pope's facial expressions.
The archbishop noted, however, "our meeting with the pope lasted almost two hours and forty-five minutes, so it is difficult for anyone to remember with precision anything that was said."