Quietly, all but unheralded, Donald Trump has begun tilting significantly away from Pakistan and toward another South Asian ally — a counterweight to China that could help tip the balance, particularly in the region’s potentially most sensitive flashpoint, the South China Sea. That enemy of my enemy is India, and it is not an inconsiderable friend to have. At the same time, though, Trump’s actions have opened another door to a resurgent China that could prove even more dangerous down the road.