Culbertson had a son, Paul Trauger Culbertson Jr., with his wife Maria Bisset Culbertson, on February 2, 1929. Shortly after, in the 1930s, the family moved to Darnestown, Maryland.[6][7]
Culbertson began serving as Chargé d’Affaires of the United States to Spain in June 1947.[1][14][15] During his tenure, he faced the challenge of negotiating with Francisco Franco's government in the aftermath of World War II.[16] Despite pressure from European allies and Spanish exiles who had stood against the fascist powers during WWII, he was instructed that the U.S. would not be seeking to remove Franco from power beginning in 1948.[17][18] This change in policy, along with 'friendly' relations by certain members of congress, made it difficult to achieve concessions from Spain in negotiations; this resulted in negotiations between the two countries seeing much debate over numerous issues.[19][20][21]
Early on one such issue was the battle between extradition and repatriation of GermanNazis in the aftermath of the war. Despite domestic pressure, Culbertson did not see the affair as integral to security, instead believing the people remaining within West Germany were a larger security threat.[22] Another was negotiating with Franco's regime over the allocation of foreign aid, the government did not want to be included under the Marshal Plan and would push back against Culbertson's attempts to liberalize the economy of the country and expand personal liberties.[23][24][25][26] One of the liberties that he criticized Franco over was the lack of religious liberty within the state.[27] He would occasionally join, then Spanish Foreign Minister, Alberto Martín-Artajo for hunting trips.[28][29]
By June 1949 Culbertson's tone shifted. He began writing back to the United States that he was skeptical of the need to export democratic values to other countries and that the Spanish people were culturally incompatible with democratic beliefs.[30] This change also became evident in his opinion on the U.S. tolerating the Franco regime, as he stated that, in his opinion, economic sanctions would be foolish and that after the fall of Franco "all hell would break loose" in Spain.[31][32][33][34] He left this position in December 1950.[1][35]