Bytedance, one of the world’s most valuable start-ups and owner of the short-form video app TikTok, has taken dramatic steps in recent months to establish itself as a credible global company.In mid May, the Chinese company named Kevin Mayer, the head of Disney’s streaming business, to fill dual roles, serving as TikTok’s chief executive and Bytedance’s chief operating officer. In recent months, the company has gone on a hiring spree to strengthen its overseas business, and has promised to limit access to overseas data for Chinese employees.  Analysts say that at a time of rising U.S.-China tensions, Bytedance appears to be moving to separate its Chinese operations from TikTok, which is increasingly popular in the U.S.  “I have yet to be convinced that there is a substantial and significant separation between TikTok and Bytedance headquarters in Beijing,” said Fergus Ryan, an analyst at the Australian Strategic Policy Institute, a Canberra-based think tank.&