When were the last subsonic turbojet-powered airliners retired from commercial passenger service?
As far as the T-104, Aeroflot retired the Tu-104 from civil service in March 1979 however it wasn't until after the Pushkin crash in February 7th 1981 that killed 52 people that the type was permanently removed from service.

Follow-up / safety actions
The remaining military Tu-104 aircraft were grounded following this accident.

Source: https://aviation-safety.net/database/record.php?id=19810207-0
The last commercial passenger flight of the Comet 4 was by Dan Air on November 9th 1980.

Comet 4s flew with BOAC until 1965 and with British airline Dan Air until 1980.

Source: http://www.bbc.com/future/story/20170404-the-british-airliner-that-changed-the-world
To answer the actual question of the last in service, that appears to be the B707 for all countries.
Trans World Airlines flew the last scheduled 707 flight for passengers by a US carrier on October 30, 1983

An era in U.S. aviation ended at 3:25 p.m. on Oct. 30, when TWA Flight 4, the last Boeing 707 to fly for a scheduled airline in the continental U.S., touched down at New York City's Kennedy International Airport.

Source: http://content.time.com/time/magazine/article/0,9171,952267,00.html
Saha Airlines of Iran was the last airline to keep 707s in scheduled passenger service until April 2013.

All flights of Iranian airline SAHA have been stopped due to its outdated aircrafts. The airline, which has been established by the Air Force of Iran, has operated for 23 years, but the Civil Aviation Organization of Iran stopped its operation due to outdated aircrafts. SAHA owns four planes, including three Boeing 707s with an average age of 36.8 years.

Source: http://www.payvand.com/news/13/apr/1165.html