Is it best to buy my train ticket in Amsterdam, or buy it here in USA before going to Amsterdam?
If you're sure about your travelling days, advance buying gives considerable discount on the fast Thalys service. If you want to be flexible, you can either accept buying a Thalys ticket the day before at the normal price or take the cheaper Intercity service, which takes one hour longer. Check at https://treintickets.nsinternational.nl/d-cobs-web/preferences.html