I can believe that some "natives" might say something as outlandish as "everything Germany," but if I were learning a language, I wouldn't want native speakers telling me that something like this is all right. That is no way to help them. And I still say that I have never heard it!
I was think specifically about "I love everything Beatles".
I was very busy at the time I answered and overlooked "love everything Germany", which I do agree is unlikely and in fact does not appear at all in a search.
The problem with that is that "everything German" would be normally be used instead, although "everything Germany" is used in advertising, as has been pointed out.
This would be much more common: I love everything English/American/French, Russian, etc.
Here you and I agree.
The use of a name is different. Now English is used playfully. I might say, for instance, "I love everything 'Geostan'," but you would have to be a bit more famous.
"I love everything Beatles" would simply mean: "I love everything by the Beatles, about the Beatles or any way related to the Beatles."
To me this is playful. The point I was making is that it is not the type of thing done by people who are not English-natives. It doesn't sound like a "foreign mistake", and although it is used by advertising, it is not limited to advertising.
You will see this construction for certain names:
"I love everything Tolkien"
"Everything Tolkien related."
"I collect everything Tolkien."
It works better with some names than others, and it's a very informal, "slangy" way of getting across an idea.
Like you I would not recommend it to someone who is just learning the basics, but we have many people in these forums who are quite advanced.
People want answers to questions such as these:
Is it formal? Informal? Slang? Wording used only by adverstising? Only by fans?
I prefer to avoid the phrase, "It's not English".
Instead, I attempt to talk about the "register" of English being used.
Fairer?
Gaer