(RNS) The Vatican's highest-ranking official in the United States, Archbishop Pietro Sambi, died Wednesday (July 27) night at Johns Hopkins Medical Center in Baltimore, succumbing to complications from lung surgery performed a few weeks earlier.

Sambi, who was 73, spent five years representing the Holy See's interests in Washington, helping Pope Benedict XVI reshape the American hierarchy through key appointments.

Choosing Sambi's replacement could be one of the most important decisions Benedict will make. The apostolic nuncio -- in effect the Vatican ambassador to Washington -- plays a central role in advising the pope on naming new bishops.

Those appointments form a key legacy for any pope, but especially for Benedict, who is 84 and has made only one visit to the United States as pontiff. The bishops that Benedict chooses to head American dioceses are central to implementing his vision for the Catholic Church in the United States, and many are sure to outlast his tenure.

The Italian-born Sambi was a career diplomat for the Holy See who served on five continents and in a number of delicate posts, including a stint as the Vatican's representative to Israel and Palestine, where he helped arrange Pope John Paul II's historic pilgrimage to the Holy Land in 2000.

In late 2005, Pope Benedict, who had been elected pontiff that April, named Sambi his apostolic nuncio to the United States. A large, gregarious figure, Sambi was known for his warmth and sense of humor.

In a 2008 interview with Religion News Service, Sambi joked that he needed a new pair of glasses when he was assigned to the United States after eight years in Jerusalem.

"In the Holy Land, everything is small, and every small thing can become a big problem," Sambi said. "In the United States, everything is huge: the country, the people, the possibility, the opportunity and the responsibility."

Sambi knew how to operate behind the scenes in the secular world as well as in the often byzantine realm of church politics. When Benedict upset many Catholics by deciding not to visit Boston -- the seat of the clergy sexual abuse scandals -- during his 2008 visit to the U.S., Sambi helped broker a resolution: the pope met privately with several abuse victims in Washington.

When Sambi wanted to deliver a message he could also do so in forthright public speeches to the U.S. bishops, such as a 2006 address warning them about the "loss of credibility in the church" in the wake of the clergy sex scandals.

Sambi's role in advising Benedict appointees to high-profile dioceses was key, and observers say his influence was seen in Benedict's selection of prelates like Cardinal Donald Wuerl in Washington and Archbishop Jose Gomez in Los Angeles. Both men will be far more visible than any nuncio ever is.

Another one of the prominent appointments of Benedict's reign, New York Archbishop Timothy Dolan, now president of the U.S. States Conference of Catholic Bishops, on Thursday eulogized Sambi as an open and affable pastor who "understood and loved our nation."

"He enjoyed everything from a stroll in the park near his residence in Washington to the diplomatic functions he attended as part of his service as the representative of the Holy See to the United States," Dolan said.

"He traveled throughout the country, often to attend the ordination of bishops, always eager to meet the faithful, and to share with them the affection that the Holy Father has for them and their country."