There are very few American singer/songwriters who’ve been able to transcend the purgatory of genre and cross over into “national treasure” territory. While debating nominees, one should consider Lucinda Williams, who has written a ubiquitous Grammy jam (Mary Chapin Carpenter’s “Passionate Kisses”), a universally acclaimed Americana masterpiece (Car Wheels on a Gravel Road), and produced a fruitful catalog that includes collaborations with legends like Ramblin’ Jack Elliott and Elvis Costello. Like a twangier Chrissie Hynde wearing well-worn cowboy boots, lost in the Laurel Canyon wilderness, Williams expertly glides between steely grit and tender grandeur, shedding tough layers to expose vulnerable heartstrings and then wrapping them back up with swathes of faded denim.