I will arrive at Terminal B at 12:30 PM via a Lufthansa flight from India after taking a stopover in Munich.And my next flight is from Terminal A at 16:59 to Indianapolis. Considering this is my first time to US, I will have to collect my baggages when I arrive at B, go through immigration, check my luggages back in and then hop on to the Airtrain and reach A. Given the time period, will it be enough for a smooth transit? Just so you know, this will be one single ticket.
As a general rule of thumb, if the transfer time wouldn't be enough to allow the connection to work in most cases, the airline wouldn't sell it to you, as they have to rebook you if you miss your plane if the queue at immigration was too long.
Having said that, more than 4 hours is plenty of time. Commonly, the minimum transfer times from international to domestic are between 90 minutes and 2 hours at US airports, and you are over that by a large margin. Also, as your plane is coming from Munich, there will be many passengers for whom the immigration procedures are relatively fast, which should help to minimize the waiting time.