According to this evening's 60 minutes episode, there were many attacks by German U-Boats on American ships in the Gulf of Mexico. Is this report accurate, and are there any other instances of under reported attacks on American soil throughout the country's combat history?
I would not call the U-Boat Campaign along the American Coast "Under reported"
It was a major event for people living along the coast, with mandatory blackouts and civilian coast patrols becoming a fact of life very quickly.
The USN had also tangled with German U-Boats before even entering the war with the destroyer USS Reuben James even being sunk while escorting merchant shipping well out into the Atlantic in Oct 1941 as part of the Neutrality Patrol.
The German Operation Drumbeat began soon after the US and Germany declared war on each other. It was the intentional surging of Type IX long range boats to the under defended and vulnerable American Coasts to prey on coastal shipping. It was a large success and from about February to August 942 over 600 ships of more than 3million tons were sunk for the loss of less then 2 dozen U-Boats. Informally the Germans named it the Second Happy Time for the ease with which they could attack targets from Maine all the way to Texas.
In the Gulf itself about 50 ships were sunk during that time. In fact on May 12, 1942 the 10k ton tanker Virginia was torpedoed and sunk by U-507 in the very mouth of the Mississippi river with the loss of 27 of the 41 crew.
There was the 1915 Vanceboro Bridge Bombing, which killed a number of people. It was carried out by German agents, in cahoots with the German embassy in Washington.
One of the men at the embassy was Franz von Papen, who played a key role in the death of the Weimar Republic and Hitler's rise to power.
The Japanese successfully attacked the US mainland during WWII, depending on how one defines "success." Balloons (unmanned) were armed with incendiary devices and high explosive bombs and sent towards US targets. They arrived in places from Alaska to the southern US and even got as far east as Michigan. While the risk of the incendiaries sparking large fires (particularly out west in the US) was real, the damage was slight overall--with the exception of one lethal attack. Sadly a pregnant woman and five children were the victims of one balloon's payload.
The press initially agreed not to report on the attacks so as to not give the Japanese information about where the attacks were successful. This ban was lifted after the fatal attack, but I would still consider it "under reported" because it doesn't usually make the list of attacks on US soil during WWII. Given the relative ineffectiveness of the attacks perhaps its obscurity is understandable.