You tell me 20 submarines operated in the Gulf of Mexico. In know nothing about this. I'm not able to imagine that one of the very little submarines of Hitler was able to cross the Atlantic, to fight there, and to turn back to Germany. But even in case it would had been so and one or some submarines had the order there to confuse the USA: This is totally unimportant in case of world war 2
As you know, I proved there were many more than 20 submarines that operated on the East Coast and in the Gulf of Mexico. You said it was impossible, proving your ignorance of WW-II.
If you had bothered to read any of my reliable sources (there are dozens) you would know that the Nazis used specially designed subs to re-supply the attack subs.
The Type XIV U-boat was a modification of the Type IXD, designed to resupply other U-boats, being the only submarine tenders built which were not surface ships. They were nicknamed "Milchkuh/Milchkühe (pl.)" (milk cows).
Type XIV submarine - Wikipedia
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