Are three year degrees from India equivalent to Four years degree in the US?
US does not have centralized rules about such things. It's in the hand of each university how they want to handle it. 

Very few US universities will admit students with a 3 year bachelors from India. You can check that by writing a mail to the admissions office of the respective university.

Majority of the universities however will not accept the 3 year bachelors. For these universities, you will have to complete 16 years of formal education(10+2+4). This means that you will either have to complete a masters degree or some additional one year degree.

Note that most of the B-schools accept Indian 3 year bachelors nevertheless.