Time to transit at Schipol

2:15 should be fine.

In a few days your travel date will be in the window to check how busy Schiphol will be. https://www.schiphol.nl/en/my-travel-day/today/departures/

The train station is directly under the airport, so your hang ups will be the timeliness of your arriving flight, immigration, and baggage claim. I have been through Schiphol many times and would probably feel ok with a 2:15 train.

Variables to consider are where you are flying from (transatlantic flight which can have delays plus volume of passengers going through passport control) plus whether you will have checked baggage. Both factors could make the connection a bit tighter. Or you could choose a changeable train ticket.

If you stick with trains operated by NS and not Eurostar your ticket is good on any train that day. Also NS trains are fixed price no reservation required on that route so you don't really need to book it in advance

The Dutch and Belgian railways introduced more direct trains between Amsterdam and Brussels last, including the Eurocity Direct: https://www.nsinternational.com/en/news/new-trains-to-belgium.

Thank you everyone! We are flying from Boston and will have one checked luggage.
I am curious if I book for the 215 pm through the NS international train, if I miss I can do the next available train?

TIA

If you buy a fule flex ticket on the ECD service you can indeed take any service on the day your ticket is valid for, so a good option when arriving by plane. You can take a later train then the one you selected, but also an earlier one.

The railways also sell non flexible tickets for those trains, these are cheaper, but only valid on the train you selected. Pay attention to the condictions.