Dissecting "That's What I Get for Loving You" by Diamond Rio

Melton waxes music nerdy about his favorite country band, the always-meticulous Diamond Rio, and their uber-bright 1996 hit "That's What I Get for Loving You".  What makes this song feel so upbeat and happy?  When is twang poppy (or pop twangy), and what does Mariah Carey have to do with it?