Some of my thoughts on this comparing of USA/PRC vs India sucking up to Pakistan:
1) US Military has a far bigger voice in American politics. No American President can be voted in, if people think he is will be soft on terror, on defense of America, and if he doesn't have an endorsement from at least a few popular retired Generals. Indian politicians on the other hand, do not allow military anywhere near politics, and the effort is to keep them down and away, even after retirement.
2) Republican Administration feel much more comfortable with the US Military, then Democrats do. Usually Democratic Presidents want to clip the wings of the US Military, and keep a firm grip on security policy. Where are the retired generals in INC? Even as BJP took over, our defense minister was George Fernandes.
3) India is a neighbor of Pakistan, with both blood ties and and ideological enmity having deep roots, unlike USA sitting on the other side of the globe, giving USA more leeway in its policies towards Pakistan.
4) A policy U-Turn takes time, and so too would it in case of Pakistan, from ally of USA to a security threat to USA. The evolution of India's Pakistan Policy too has taken time - from less Dhimmi to more Dhimmi!
5) USA has budget deficits, and still a long list of military targets - Afghanistan, Iraq, Iran, Syria, NoKo, and somewhere at the end, also comes Pakistan. Right now, Americans are sitting in Afghanistan as hostages, and as such Pakistani perfidy is biting them, so there is some discomfort with Pakistan. If Americans were out of Afghanistan, and if Americans had finished off a few top terrorists - Zawahiri, Haqqanis, etc. why would America still be pissed off at Pakistan? Pakistan is then becomes less interesting - both as ally but also as foe, unless their global terror does not die down! India too has to think about the threat of China when dealing with the threat from Pakistan, but Pakistan still needs to be taken down first, as Pakistan is also China's paw! So it should remain India's primary focus to be dealt with in the short term. USA may not see the situation in a similar way!