Japanese people celebrate many special holidays. But it's just an excuse to party.
「日本人はたくさんの日を祝う。それは騒ぎたいだけ。」は英語で「Japanese people observe many special days. But it’s just an excuse to celebrate.」という表現が良いと思います。
「クリスマスだけでなく、ハロウィンにバレンタイン、日本では特に若者が色々な日を祝っています。」Not just Christmas, but also Halloween and Valentine’s Day; the young people in Japan especially observe various holidays.
「祝っているというか、彼らは（もちろん自分も）ただ騒ぎたいだけです。」I say people observe the holidays, but really it’s just an excuse for everyone (and of course, me too!) to drink/party.
Japanese people celebrate all kinds of days—mostly just as an excuse to have fun.
**Japanese people celebrate all kinds of days—mostly just as an excuse to have fun.**
**In Japan, we celebrate a lot of days, but honestly, it's more about having a good time than the meaning behind them.**
「祝う」は *celebrate*、「騒ぎたいだけ」は直訳すると *just want to make noise* になりますが、日常英会話では *have fun* や *have a good time* を使うと自然です。また「口実として」というニュアンスを出したいときは *as an excuse to〜* を使うのが効果的です。
アメリカ合衆国 
