There are documnets stating the Nazis managed to sink several mexican oil tankers in the mexican gulf, preventing them to reach the US. How did Nazi Submarines managed to get that far from Europe? Could they have orchestrated attacks on the US from there?
The Type IX U-boats easily had the range to operate in North American waters (the IXA had a range over 10,000 nautical miles, and the IXC over 13,000 nm). North America was outside the normal range of the Type VII U-boats.
With US entry into the war, the German navy planned to make U-boat attacks in US waters with the maximum possible number of U-boats (Operation Paukenschlag AKA Operation Drumbeat). At the time, only 20 Type IX boats were operational, and only 6 were available for the start of the operation. One of these 6 boats developed problems, and needed repair. These 5 U-boats left their ports in France for the US in the 2nd half of December 1941. From mid-January to early February, these boats sank 25 ships, and headed for home. Before they left US waters, the next wave of U-boats had arrived.
Due to the small number of Type IX boats available, extraordinary measures were taken to let Type VII boats reach the US - some of the fresh water storage was converted to hold diesel fuel, and provisions were stored in any space available (including one of the two crew toilets).
In May 1942, Type XIV U-boat tankers (Milchkühe, or "milk cows") were operating in the Atlantic, refueling and resupplying both Type IX and Type VII U-boats, letting them operate in the Caribbean and in South American waters.
How close did U-boats get to North America? U-123, one of the original Drumbeat boats, entered New York City harbour on 15th January 1942. Many ships were sunk within a few miles of the coast; U-123 sank a tanker 2 miles from Jacksonville, Florida. U-boats operating in the Gulf of St Lawrence and the St Lawrence estuary. U-518 landed a spy near New Carlisle, Quebec (the spy was captured soon after landing). U-537 installed an automatic weather station (Wetter-Funkgerät Land-26 "Kurt" AKA Weather Station Kurt) in northern Labrador, Newfoundland in 1943 [1]. After the German surrender, U-1228 sailed into Portsmouth, New Hampshire to surrender, U-889 sailed into Bay Bulls, Newfoundland, and U-190 sailed into Bay Bulls, Newfoundland (and served for the next two years in the Canadian navy as an anti-submarine warfare training ship). By the time of these late-war patrols, the Germans had lost their U-boat bases in France; these boats sailed from Germany and Norway.
They got close to South America, too - e.g., U-507 was sunk off the coast of Brazil.
Other U-boats also operated far from home. Eleven operated in the Indian Ocean (Operation Monsoon). Four U-boats were to operate in Australian and New Zealand waters, from Japanese bases in Malaya and Indonesia. The first two of these boats were ambushed by Allied submarines alerted by intercepted and decrypted signals, and were sunk in Indonesian waters on the 2nd day of their patrols (U-168 by the Dutch submarine Zwaardvisch, and U-537 was sunk by the US submarine Flounder, one of three hunting for her). U-862 was more successful, surviving a three-month patrol in Australian and New Zealand waters, but with only two sinkings. The last U-boat, U-196, disappeared, fate unknown. For more on these last operations, see
[1] The military purpose of Weather Station Kurt was disguised by American cigarette packets and a label claiming ownership by the "Canadian Meteor Service" (despite Newfoundland not being part of Canada). Weather Station Kurt was discovered in 1977 by a geologist - the disguise worked, and he assumed it was a Canadian military installation. Shortly after, its existence was learned about from the papers of the German meteorologist who had installed it, and it was recovered by a Canadian Department of National Defence historian in 1981.