Given the apparent) ease with which illegal aliens come and go in the USA, why was it so hard for the Germans to have spies here during WWII? There was a significant Geman-American population, and lots of places to disappear in to. Yet, I don’t think the Germans were able to do mush here. Was this also the case for Canada? It seems to me that with its huge Arctic coastline, Canada would be an ideal place to land agents (from a submarine). Were there any spies that got in that way?
Finally, I read something years ago-about an abandoned house, in a remote part of the Maine coast-some people bought the house, and discovered evidence that it had been used during the war, as a spy hideout (German newspapers and documents found from WWII)-anybody know about this?
The US Naval Historical Center concludes as follows:
The R.S.H.A. refers to the Reich Security Main Office.
One presumably informed opinion which agrees in part with this conclusion is that of Cambridge Professor Christopher Andrew, official historian of MI5:
If Prof. Andrew is anywhere close to being correct it seems that German spies in Britain were about as successful as they were in the US.
Is the old tale of German spies being caught because they didn’t know what French Toast was actually true?
Probably easier for them to mush in Canada. If they could get the dogs. 
Note that the head of the Abwehr hated Hitler and was part of the plot to overthrow him, so perhaps this was one of the reasons why the Abwehr didn’t do so well in the USA.
My mind’s still swimming at the logical jump from illegal aliens to Nazi spies.
I don’t see the logical jump, personally. 
Note that spies, to be effective, have to be getting the info they acquire back to their spymaster. That implies regular meetings & contacts, and traveling back and forth.
Most illegal aliens are coming here to work, intend to stay here long term, and aren’t interested in traveling back to their home country. So obviously, they have much less risk of detection.
Not an agent per se, but the Germans did land a weather station in Labrador (technically part of Britain at the time) by U-Boat. It wasn’t actually found until 1981.
That said, the “huge Arctic coastline” would be a pretty poor place to land an agent; Newfoundland, with its many military installations during the war (Canadian, American, and British) would be a much better place, but then you’d have to teach a German to speak like a Newfoundlander. Imagining that particular mixed accent makes my head hurt.
The Brits were decoding most of the Germans signal traffic which resulted in them catching the early German spies who they then offered the choice of execution or working for the U.K. intelligence services .
The “in place” German spies arranged the landings of later enemy agents who were captured immediatly on landing and who were offered the same options .
As a result ALL German agents sent to the U.K. were captured.
Its only a guess but interception/decryption of Abhwer signal traffic may have given away agents sent to North America ,information which the U.K would have undoubtedly have passed on to the U.S. even before their entry to the war.
All the stories about German agents being captured because they started snacking on Knockwurst on British busses and the like were fabrications spread around by the U.K. intelligence services after the war to prevent the Soviet Union from realising that we had the ability to decypher messages encripted on the Enigma Code machines.
The Russians had adopted variations of this machine for encoding military and intelligence messages during the cold war.
It is alleged that the so called "Red Orchestra " Russian spy ring operating in Germany and Switzerland during the war was in fact a British fabrication used to facilitate the passing of useful information to Stalin without letting him know that we could decode the enemies traffic,that and the fact that he treated with suspicion any information that openly came from us .
Here is a more filled out story on Gimpel - he is referred to in Chez’s link. He came ashore in Maine, but didn’t stay long. I think rightly, he is considered the most successful of the spies landing in the U.S. The FBI knew he was probably here, but he wouldn’t likely have been caught when he was if he hadn’t brought along the Oswald of his time (Defecting/Defecting back). Note: he was here to sniff out the Manhattan Project and him getting the info and getting the info back to Berlin strikes me as unlikely - so I don’t think his mission would have worked.
OTOH the saboteurs that landed in Flordia were the gang that couldn’t shoot straight … but had a mission that actually could have succeeded.
I think partially the answer to “why not do this more” is that the U-Boats were a valuable and increasingly scarce resource better used hunting allied shipping and not running risky close to land missions to land a couple guys who may or may not ultimately do as much damage as 3 well fired torpedoes.
I have anecdotal evidence that a Fifth Column unit landed on the Jersey Shore and were running amok for all of a few days. . . until they broke up.
Again, it’s anecdotal, but give me some time to find a cite or two. Grandpop (rest his soul) didn’t fib, and I remember him showing me an old article from somewhere in Cumberland County.
Tripler
Yup, I spent my summers in South Jersey.
A long time ago, I read a tale of a captured or sunk U-boat where the good guys found theatre ticket stubs from a production in New Orleans on the officers’ persons. I might have seen this in a movie.
That wasn’t true either, right?
This might have been based on operation"Mincemeat"which was an operation by the Brits to mislead the Germans into thinking that the Allies were going to attack and occupy Crete from N.Africa rather then Sicily the real target.
They left a corpse dressed in a Royal marine officers uniform with a briefcase full of documents in the sea (from a submarine)where it would be washed ashore in Spain which was technically neutral but was in fact all but an ally of the Axis powers .
As predicted the Spanish covertly allowed the Germans to inspect all the documentation on the body before handing it over to the British embassy in Madrid.
To convince the Germans that the body was a real person and not a ruse its pockets contained “love letters” from its girlfriend,a letter from its tailor reminding of an overdue bill and a ticket stub from a London theatre performance.
If you are in interested in reading more about Lust4Life’s Operation Mincemeat there was a book and later a movie about this called The Man Who Never Was .
**
Tripler** if by “run amok”* you mean had their equiptment immediately confiscated upon landing, their U-Boat sighted at drop off and dejectedly turning themselves in … then there were guys who landed on Joisey
**Which is less exciting and lurid than a Local newspaper would make the story I bet
*
**T_Square **as far as I know there were three accomplished landings of spies in the U.S. by U-Boat
1942
One Team of saboteurs in Jersey and one in Florida (part of the same Operation)
1944
Gimpel and nut in Maine on a spy Mission
In addition Oskar Martel was pulled from a sunken U-Boat with a ton of U.S. cash and was likely on his way here.
This fact can be postulated as part of the problem later in the war, but in the early years when things were going well for the Nazis, Wilhelm Canaris seems to have been an enthusiastic supporter of the regime.
German espionage did take advantage of lax U.S. security in prewar years and resulted in the theft of a number of military secrets (including the Norden bombsight). It also featured blundering stupidity, such as the recruiting under threat of American (and German native) William Sebold, which led to his working as a double agent and the break-up of the Duquesne spy ring in 1941.
wiki:
In 1937 he was still a supporter of Hitler, considering him to be the only solution against communism and a hope for the revival of Germany as a nation.By 1938, however, he had realised Hitler’s policies and plans would bring catastrophe to Germany and secretly began to work against the régime. His personal style as a gentleman could not tolerate the gangsterism of most of the Nazi party members. There is a letter that remained from a Spanish contact he had that confirms clearly his opinion against the Nazi regime. He tried to hinder Hitler’s attempts to absorb Czechoslovakia and advised Franco not to permit German passage through Spain for the purposes of capturing Gibraltar. It has been written that all of Franco’s arguments on this stance were studied and dictated in detail by Canaris, while at the same time an important sum of money had been deposited by the British on Swiss accounts for Franco and his generals to further convince them to be neutral.[2]*
So, it appears Canaris- and most of the world mind you- was taken in for a breif time, before Hitler’s true self showed itself. And Canaris turned against Hitler long before the US entered the war.