The paper analyzes the loanwords from the American English the Japanese language considering the diachronic perspective in relation to historical and socio-cultural processes that took place in Japan. The periodization of the waves of penetration of such borrowings into the Japanese language system considering socio-cultural shifts in Japanese society is offered. The first wave, which can be dated from the end of the XIX cent. till 1930s, consists of the first borrowings-Americanisms, the penetration of which into the Japanese language is connected with the first systematic contacts between Japan and the USA, as well as the humanitarian aid of the USA of Japan after the Great earthquake of 1923. The second wave can be dated from 1940s till 1980s; during these years in the context of post-war American occupation, Japan became obsessed with American mass culture and, consequently, spread its own mass culture created on the basis of an American one. In the Japanese language system, this stage is characterized by an avalanche-like enrichment of the gairaigo lexical layer by borrowings-Americanisms, followed by the "digestion" of foreign words and their deeper integration into the system of the national language through the creation of pseudo-English words called waseieigo, as well as the spread of abbreviation. In the field of linguistics, the second stage is characterized by the beginning of scientific understanding of the significance of borrowings-Americanisms in the Japanese language and the analysis of the destructive role of these units for the language culture. The third wave of penetration of American-English borrowings is believed to be related to the proliferation of the Internet, the main language of which is English; accordingly, this stage can be dated to the 1990s until now. The main feature of the last wave is the adaptation of borrowings to the needs and norms of the national language, resulting in the activation of hybrid word formation and the creation of mixed units consisting of either a Japanese root and a borrowed affix, or vice-versa, or shortened foreign and Japanese words (hybrid abbreviation).