I have a German friend who plans to take a trip to the US this summer. She will visit her friends in Montreal first. After a week or two, she plans to ride Amtrak from Montreal to New York City. When the train crosses the US/Canada border, how do they handle immigration & customs? As a German citizen, she doesn't need a visa to visit the US, but I imagine that it's a little more complicated than the process for US & Canadian citizens, no? Last but not least, does the train wait until every passenger has cleared immigration before it leaves from the checkpoint? Any advice appreciated!