The following is from the NW website and states clearly that the minimum time between flights International to Domestic is 60 minutes. You have 65 minutes between planes. If you are sure that you are going to be "delayed" by customs my guess is you will NOT make your flight.

fhttp://www.nwa.com/plan/guide08.html

Is the "connect time" built into my reservation?

Minimum connect times that allow you sufficient time between flights are factored into Northwest's reservation system. If you are concerned about the connect time between flights, please ask about it when you make your reservation. Northwest's minimum connect times* are:

What happens if I miss my connecting flight?

On occasion delayed flights can result in our customers missing their connecting flights. If this happens, a Northwest Customer Service agent can help re-accommodate you on another flight.