The correct term is "life expectancy at age 0.
This "life expectancy" is calculated for each country, i.e., for Americans in the U.S. and for Japanese in Japan. According to 2023 data from the Ministry of Health, Labour and Welfare, the "life expectancy" of a 0-year-old Japanese child is 87.14 years for a girl and 81.09 years for a boy. In addition, according to the average life expectancy of countries around the world published by the World Health Organization (WHO) in 2024, Japan ranked first for women, second for men, and first overall for both sexes combined. Japanese people are the longest-lived people in the world.
By the way, how long can we expect to live? This is called the "maximum life expectancy," and various studies and surveys have been conducted. Some reports indicate that 150 years of age is the limit. Incidentally, the longest person in the world so far is a French woman who has lived to be 122 years old.

(Updated April 10, 2025)