Probably because America became a worldwide technological (and cultural) force. In Japanese, importing from the Europeans began in the 16th century, from the Portugese (Tabaco, Pan). It's much easier to import loanwords into a language that already has a tradition of bringing words into the language (wholesale, in the case of chinese->japanese) than one that is used to sandbagging the language against outside influence. Witness the difference between French and English (to the extreme case of French-Canadian, where they even made Arret signs, even though Stop is a perfectly good French imperative, and stop signs in france say "stop").