AMS has only one big(gish) building, even though they call it two or even 4 terminals.
You can walk within the building from one terminal to the other both before and behind security.
If the flights are bought on one ticket, the luggage will be booked through and she will not need to collect it and re-check.
From the arrivals area she will be directed to the transfer option and not pass through customs.
In the transfer lane she will pass through exit passport control, and there is a Global Blue VAT reclaim desk at next to gate F-3 to claim back sales taxes which is open from 7:00 AM till 8:30 PM daily.
(If she does go out of the building she will pass through customs but that is not much, just the green and red lanes. On the way in she would then pass through exit passport control.)
The exit passport control is a part of immigration, as a departing USA citizen she should get a stamp as matter of fact. Only if she has been in Schengen more than 90 days or when the entry stamp is not clear she is likely to be asked questions.
Going to the USA she may need to go through security but it has been a while since I last done that and Schiphol has changed the security set-up a few times over the last years. (In a now deleted answer @Henning Makholm mentioned that there is no additional security check for travelers from France.)
In the answer by @mts you can see he had an extra interview before boarding and his passport and boarding card did get an extra inspection.
The USA seems to require extra procedures which other countries do not deem needed. So expect an extra inspection, either an interview or an extra security check, but as USA citizen it should not be difficult.
In AMS English is the first language, Dutch the second and you will find many employees who will have a third and fourth language. All signs are in English first and public anouncements, including gate information, will be in English, Dutch and often a third language.
AMS has the tradition of anouncing gate information early, for USA flights that will be hours or even days before the flight. So no waiting in lounge staring at the screens, the gate is printed on the boarding pass or at least already on the screens when you first look.
Your wife will not have to worry, she will likely feel at home in that airport.