you mean not china, and not even in China's "sphere" of influence.
also none of those nations are particularly under the US's sway. Indonesia? Singapore? Mayalasia? Thailand? We don't have an operational naval base anywhere in the area. The Phillipines (1,500 miles) or Diego Garcia (1,800) would be the closest. China itself (1,200) would be closer to the Malacca Strait than we are. The phillipines we don't even have an open naval base, only air fields.
Those islands are there to steal from their regional neighbors. not because we are some existential threat to Malacca.