If you have a US passport, legally thats all you can have,
This is true for all other cases, but very importantly, India does not recognize this for people who have Pakistani origin (i.e. people who have anyone in their parents/grandparents/spouse who were born in Pakistan).
It does not matter if you have never stepped foot in Pakistan or only have a US passport.
India does not recognize you as a US citizen if only one of your grandmothers is from Pakistan, and all other grandparents/parents have never stepped foot in Pakistan. India will recognize you as a Pakistani citizen ONLY.
This is a very bad rule, but its unfortunately true. India will only recognize OP as a US citizen if he or she can provide a "renunciation certificate" from the embassy of pakistan formally confirming that they have renounced their pakistani citizenship (it does not matter that they never had it, india thinks they did because their parents/grandparents were from there). Looks like a company letterhead works also from a post above, but I'm not familiar with that rule.
This rule for US/UK citizens based solely on past origin has been a huge hassle for ~10 years now.
Alternatively, OP can lie on the e-visa application and say that his parents were born in "British India" (before the partition). This way OP can apply for an indian e-visa like any US citizens. But if you get caught for any reason whatsoever you spend your life in indian jail so .....