Earlier quoted context omitted.
The US isn't interested in picking sides. Historically it has tried to be friendly with both (though that hasn't always been easy).
"However, Pakistan was a valuable diplomatic partner, and its government helped the United States achieve a rapprochement with the People’s Republic of China in the early 1970s." "U.S. prestige was damaged in both nations, in Pakistan for failing to help prevent the loss of East Pakistan and in India for supporting the brutality of the Pakistani regime’s actions" https://history.state.gov/milestones/1969-1976/south-a…
https://en.m.wikipedia.org/wiki/The_Blood_Telegram:_Nixon,_K...
It was an active decision by the US.