Short answers, pulled from the story.
Pactomania describes the intense period of American treaty-making between 1945 and 1955. The term appeared in a 1955 article in The New York Times to capture this specific historical era.
John Foster Dulles served as Secretary of State under President Dwight D. Eisenhower from 1953 until his death. He helped create the UN Charter in 1945 and SEATO in 1954 while proposing the Northeast Asia Treaty Organization before shelving it for bilateral alliances.
Twelve members signed the North Atlantic Treaty in Washington DC during 1949. The United States, United Kingdom, and Canada began brainstorming the organization earlier that year to protect nations from potential Soviet invasion.
The US cut ties treaty-wise with New Zealand following that decision when New Zealand banned nuclear weapons in 1984. The alliance functioned as mutual aid rather than strict defense but remained active until that ban occurred.
SEATO officially created itself in Manila, Philippines during 1955 with headquarters in Bangkok, Thailand. The organization split in 1977 despite its underlying collective defense treaty remaining in force for US-Thailand relations.