Charles Bronson's character is called Link - which is the German word for 'Left' The man who betrays him is 'Gauche' - which is the French word for 'Left'.
The Japanese Ambassador refers to the emperor as the "Mikado". This term originated with the Gilbert and Sullivan operetta of the same name and became widely used in the West in reference to Japanese culture. No such term existed in Japan until after the operetta became internationally famous in the 1880s; well after the time-line presented in Red Sun.
This story takes place around 1870. During the train robbery, several calvary soldiers are shown with foreign type bolt action rifles. The US calvary troops were not issued bolt action rifles during this period, but were equipped with either lever-action Spencer carbines or single-shot Sharps carbines, with single-shot "trap-door" Springield carbines being introduced in 1873.