Maybe I can help to debunk the Monti myth.I did some reading up on this a few years back when I was "researching" British and US citizens in the SS.
In reality Monti was never 'used' by the Germans. Although Monti defected for pure ideologic reasons, the Germans never trusted him and put him on a side track. He certainly never commanded an SS unit. Also the notion that "hundreds" of Americans were in the SS is myth. So far, I believe, 5 cases are documented of which only one saw actual combat with a German SS unit. Of course there were a lot more German-Americans in the German armed forces at the time. (See Band of Brothers, part "Carentan". And I believe forum member Sapper Brian also met an American-German in German uniform in Normandy)
The Germans did try to recruit from POW camps but were unsuccesful in doing so.
The 'largest'contingents were Brits and that unit never numbered more than platoon size. Also this unit never saw action as a SS unit or frontline unit. Some men were used as drivers behind the lines for SS units, but they were found to be inadequate for the job and they were subsequently sent back.
For more info on Brits in the SS; Adrian Weale's "Renegades" and "I Killed To Live" by Chapman (who was British Free Corps himself, but the book is the biography of another brit in the SS - read the book and you'll find that it should be taken with a grain of salt)
If I have time (or maybe Kai

) I will try and see if there are some on-line sources. Although it must be noted that many on-line sources on this subject should be considered humbug.