Apostile is good to have but not mandatory for US Citizen
The attestation or power of attorney process is same for US citizen as well, except that ‘Apostile’ is good to have before going to Indian embassy for attestation.
Legally, Indian Embassy Attestation Not required if Apostiled
Technically and legally, a US citizen only needs to get the PoA apostiled from his/her state of secretary and that’s enough.
But, to be very frank, In India, they may or may not accept only the apostiled document.
USA and India have an agreement where an apostiled document is legally acceptable in courts and all government offices of India.
But, The Indian consulate website itself mentions somewhere that it is advisable that you get documents attested as the Indian Registrar’s office (where you would need to register the PoA in your Indian state) may not know about the apostiled rule and hence may not entertain your request!
So, I would also suggest you to get it attested before sending it to India, just to save time and extra hassles there. Otherwise, you don’t really need it.