I am a US citizen and recently signed up for Global Entry. One of the benefits is a special card that one can use in NEXUS or SENTRI lanes when entering the US by foot or car, which could result in faster service.
My understanding is that I can also use this card to enter the US by bus or train, but in this case, does it have any advantage over using a passport or passport card?
For concreteness, this would likely be on either Megabus or Amtrak, entering the US from Canada at Niagara Falls. I don't know what the immigration procedure is like on those services.