The definition of the whole genre "Alternate History" is that you are mostly trying to be as realistic as possible, except for one or more historical events. It's completely up to you what those details are and to what extent you exactly want to change reality. If you want a newspaper to talk about Germany attacking the United Stated then go ahead and do that - just be aware that your readers will likely have some knowledge about the real events and might pick up on these differences, which means that you should either talk about them in greater detail later in the book or treat them as a sort of "Easter-Egg", a little detail that some people might pick up, but that is irrelevant to the overall story. The reason for placing Easter-Eggs in your story would be to give the readers that look for them a few things to talk about - it should be a few things, not just one - and you should make it obvious that this is an Easter-Egg. Most of the time you wouldn't do something like this in a book.
You could of course just state that the newspaper article said that there was such an attack and later you explore how this specific newspaper was often accused of false or not-completely-true news. This has to fit in the story however.
All in all it's completely fine to change little details in this genre, but if you don't want to do something with it you should leave it out. Either it plays a role and is an intended difference, or it's explored to be at least not-completely-true or it's treated as a part of multiple little Easter-Eggs that you want your readers to find so that they may find out some hidden information for example - but you should not just put in a little difference, just for the sake of having a little difference in your book.