The arrival of China in South Asia, the withdrawal of the U.S. from the region, and India’s tilt to the Indo-Pacific have shifted the regional balance of power in Beijing’s favour. Sensing this new power equation, South Asia’s smaller powers, India’s neighbours, are engaged in a range of strategies: balancing, bargaining, hedging and bandwagoning. India’s smaller neighbours seem to find China as a useful hedge against India, for the moment at least.
I'm not sure what withdrawl they mean. The US withdrew from Afghanistan, but that is clearly Central Asia and not South Asia (unless it's defined differently in India?).
The US has withdrawn from other regions, especially the Mideast, in order to focus on China. But the US very much considers the Indian Ocean as part of the competition with China (usually using the term 'Indo-Pacific'; even the military command there is INDOPACOM); I'd be surprised if it ceded South Asia to China.