Best of what?

I earlier noted that Otto Penzler said that Charles McCarry was the best ever spy novelist. Penzler should know as he is the owner of the famous Mysterious Bookshop of NYC. After I read that I thought, is that such great praise? Aren't the good spy novelists British? I'm thinking of people like Le Carre, Maugham and Greene. Sure, we have Alan Furst on this side of the Atlantic, but he is mostly a noir sort of writer. Being the best American spy novelist is like being the best metal band from Nebraska, not a lot of competition.