After successfully importing anime such as Gigantor, Astro Boy, & Speed Racer, and movies such as "Godzilla" to America, the Japanese brought over one of their first live-action adventure series not named Ultraman.
Giant Robo launched in 1967, and was imported to the US 2 years later by American International under the title, Johnny Sokko & His Flying Robot. Research says it was well received here, but I have no recall of ever seeing it on local or cable channels. The series lasted just 1 season, predictably, and the last few episodes were cobbled together into a feature film released in 1970.
Hulu brings us the opener. The 1969 copyright date is for the American issue.