Couple of things pointing to this being about John Mayer...
Story of Us: "So many walls up, I can't break through."
Heartbreak Warfare: "God only knows how much I'd love you if you let me / But I can't break through it all"
Story of Us: "The battle's in your hands now, but I would lay my armor down if you say / you'd rather love than fight."
Heartbreak Warfare: "I swear to God we're gonna get it right / if you lay your weapon down"
And, to me "Now I'm standing alone in a crowded room" sounds very similar to "My dear we're slow dancing in a burning room"
Couple of things pointing to this being about John Mayer...
Story of Us: "So many walls up, I can't break through." Heartbreak Warfare: "God only knows how much I'd love you if you let me / But I can't break through it all"
Story of Us: "The battle's in your hands now, but I would lay my armor down if you say / you'd rather love than fight." Heartbreak Warfare: "I swear to God we're gonna get it right / if you lay your weapon down"
And, to me "Now I'm standing alone in a crowded room" sounds very similar to "My dear we're slow dancing in a burning room"
Just my take