Though it did cause some confusion among the Italians:
“Is that a U-boat?”
“No, that’s not-a my boat.”
I’m not sure this is a genera trait of English. NATO has developed elaborate systems to give English-language names to weaponry of non-NATO countries. Such as, for example, Mike for the Soviet nuclear submarine that was called Plavnik in Russian, or Fulcrum for the MiG-29, or Fagin for the Chinese Chengdu J-20.
It’s not just used by the German Navy for its own submarines; it’s also the generic German word for all submarines, including those of other countries.
Groucho: “Go along the viaduct.”
Chico: “Why-a- duck? Why-a no chicken?”
What a polite term for those that skulk around and sink ships without warning.
There was a use for a term for a German submarine, because they were using a lot of them, to great effect. There wasn’t much use for a term for any other nation’s submarines, because they weren’t using them so much.
“Is that a U-boat?”
“No, I’m just looking”
Only in Central Park Pond. Before WWI subs were model boats, many of them remote controlled. Tesla demonstrated one in 1898 and they took off from there. When the word submarine or sub was used people in America certainly - thought of the homegrown and totally peaceful boating community rather than warships. One major reason why a foreign term had terrific propaganda effect.