I wish to strongly endorse the comments of others that 90 minutes is NOT enough time to allow to clear immigration/customs, change terminals, go through security again, and then get to your gate

Is it theoretically possible that it could work? Yes. Would I want to bet on being able to do it? No, especially at Newark, which is one of the more inefficient airports in the USA.

Change your flight to allow more time, if that is possible. If not, and your entire segment is on the same record, United might try to help you on to the next flight if there is one, if it has space, and if you get a good agent -- but you run the risk of being stuck with an overnight stay at Newark at your expense. The area around Newark Airport is not a great area to have to spend the night.