Maybe JRRTolkien, George RR Martin, or J.K Rowling might have passed him but it’s highly doubtful. ( Tolkien maybe.) John Steinbeck of course was wonderful, and Mark Twain, as well as Ernest Hemingway, and possibly one of the beat generation writers like Allen Ginsburg, but still not the level of popularity as Burns. I do like Vonnegut quite a lot, and think Hunter S Tompson, and William S Burroughs are quite good and popular, but doubt that their sales exceed 100 million. Steven king Allan Moore and Phillip Larkin all have achieved greatness with their works I’m not sure of ( sales wise at least.) HP Lovecraft though has quite some influence! and as you can see I’m pretty sure he’s America’s most influential writer of the last two hundred years, but I couldn’t tell you sales figures.