New Delhi, Aug. 8 -- For over three decades, since Prime Minister P.V.Narasimha dismantled India's "license raj" and made a distinct diplomatic tilt towards the West, India's slow but steady closeness with the United States has been one of the few constants in the volatile landscape of global geopolitics.

From the ruins of Cold War non-alignment to the glow of civil nuclear recognition, Washington and New Delhi forged a sometimes uneasy but durable bond, an alignment anchored in shared democratic values, converging strategic anxieties, and a common adversary in a rising China.

Now, with just 21 days left on the calendar, Prime Minister Narendra Modi stands at the edge of that carefully constructed bridge, watching it catch fire-tweet by...