Why did America and Britain recognise Bangladesh so quickly post independence while China took time? Also why did Japan recognise Bangladesh so quickly unlike the other East Asian countries?

So I’ve always been wondering about this. Both the US and UK we’re almost fully supporting Pakistan during the war, but as soon as Bangladesh gained independence, the US and UK recognised Bangladesh in 6 and 2 months time respectively. Why did they change their position so quickly? Also what made Japan so keen to recognise Bangladesh so quickly while China and Korea really took their time?