I am reading a book which is quite difficult for me.
I attached a page in which a Japanese guy who is living in the USA is coming back from a trip.
I have difficulties to really get the point of the whole conversation on this page. What exactly is the problem?
The Japanese guy thinks showing his passport is enough because he lives in the US, but the immigration officer says he has to go through the immigration check. Starting from the sentence in the middle of the page 「向こうで出入国手続きをした」 I get lost.
What is 向こう referring to here? The second sentence after this one the Japanese(?) asks why he wasn't told that(what?) before. This mention of Mexico doesn't make much sense to me either.
I would appreciate hints what is going on. I am slightly confused.