Brian May has given a figure of 180 million worldwide which is probably the best estimate you will find. The only place you can find a comprehensive listing of top selling artists worldwide is Wikipedia and their numbers are a bit dodgy and from such a disparate collection of sources that they are basically useless. The problem with "worldwide sales" is they are not tracked well in many places.
For US sales, a good source is the RIAA website, but that is only for the US sales. They list Queen at 32.5 million in the US.
On a side note, The Eagles currently hold the record for the most sales of a single album in the US for "Their Greatest ts 1971-1975" with Michael Jackson breathing down their necks in the #2 spot with "Thriller", both having sold in excess of 29 million copies. Michael has been gaining since his death and will likely end up passing them soon. (Estimates of worldwide sales of "Thriller" are in excess of 70 million and since the Eagles biggest sales are probably by far in the US, Michael probably beats them handily internationally.) The next closest album is Led Zeppelin "IV" at over 23 million so it looks like for the foreseeable future The Eagles and Michael will fight it out for the top spot.
I'm guessing that number would be very high. But, I'm not sure if 300 million would be correct. I looked in Guiness to see if there was anything there, but, Queen was not mentioned.
But, I take that with a grain of salt, because most of the acts that are on the lists are ones that are still touring. And, there was no category for most albums sold.
But, there was mention of The eagles held the record for the greatest single album ever sold in the U.S. at 25 million. But that is so wrong when Michael Jackson's Thriller sold over 33 million.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.