system
Given the following post, respond as if you're commenting on Reddit:
human
[Indiana Jones] Legal/Political Ramifications of the events of 'The Last Crusade'

The Last Crusade takes place in 1939, and it seems obvious that it's pre-Poland Invasion. 

However, given that the political situation between Nazi Germany and the rest of Europe, would travel to/from Germany have been as easy for Indy who was presumably carrying an American passport?

The US embassy in Germany had been closed since 1938, but when Indy, his dad and Marcus get back to the States, surely their revelations would be startling to the American leadership who would be debriefing them, right? 

Speaking of, how did they get back to the US? The French ceded the port of Iskenderun (presumably near the Canyon of the Crescent Moon, given it was the city where Marcus was captured) to the Republic of Hatay in 1939, so did they just get aboard a French merchantman?
gpt
Indy carries several different passports for traveling. Treasure hunting is a dangerous game, and Indy is not always doing it legally, so he often travels incognito to avoid undue attention. Plus there is the difficulty of trying to get treasure through customs, so he may avoid traditional commercial travel when it's convienent to do so.

As for "spying" on Germany we find out in The Crystal Skull that Indy joined the military during WW2, so it's likely he was recruited specifically because of his insider knowledge of the Nazi military and infrastructure.