How much layover time do I need from disembarking from flight from USA to embarking on a flight to Amsterdam? I have one hour and a half to get off the plane from the USA and to get on a plane to Amsterdam. Is this enough time?
If both flights are on the same ticket, you should be fine, as long as your incoming flight is on time. You won't need to go through immigration or collect your bags. Dublin Airport has a connections guide, which says that it will take at most 20 minutes to walk to the gate. Boarding for a short-haul flight such as Amsterdam will probably begin 30 minutes before the scheduled departure time and end ten minutes before. If your incoming flight is delayed, the airline will put you on the next available flight.
If you have two separate tickets, you don't have enough time. You'll need to go through immigration, collect your bags, check them back in (before the check-in deadline, which could be as much as an hour before departure), go through security and get to your gate. If you miss the connection, the airline for the second flight might put you on a later flight but they're entitled to say "Tough luck – it's your responsibility to get to your departure airport on time and, for us, your departure airport is Dublin."
if both planes are in the same terminal it should be no problem
There are only 2 and takes 5 mins to walk between terminals but sometimes there can be a 20 min walk inside terminal 1
Try to be off the plane first if you need to go through emigration, there can be only 1 or 2 desks for non-eu passengers and it can slow you down, so try to sit at the front of the plane if you can choose your seat for the inbound flight