"Rain makes corn, corn makes whiskey
Whiskey makes my baby feel a little frisky
Back roads are boggin' up, my buddies pile up in my truck
We hunt our honeys down, we take 'em into town
Start WARSHIN' all our worries down the drain
Rain is a good thing..."
That song deserves a mention here, not because of the mispronunciation of a word (although that would be reason enough), but because the lyrics that you sampled here trot out every tired old stereotype heard in country music since the beginning of time.

I'm surprised that he didn't also trot out that "I'm more country than you" b.s., but maybe with these lyrics, he didn't have to!

There's also something I call "Artificial Hillbilly Flavoring" in the voices of many young, mostly male country singers. They have a nasally twang and various mispronunciations (they are artificial because you can hear the emphasis they make in their mispronunciations of these words.) On top of "warsh", there's "won't" for "want" and "thang" for "thing" (evidenced in Mark Chesnutt's otherwise excellent rendition of "I Don't Want To Miss A Thing")
The "I'm more country than you" BS is a byproduct of the "I'm more ghetto than you" BS that came from hip-hop. But like in any real life situation, if you actually put these posers on a farm (or in the deepest, most crack infested ghetto) the illusion quickly disintegrates into "I wanna go home" once they find out there's (still) no mobile web signals in many rural farm areas (or their computer/cell phone gets stolen in the ghetto) and they can't connect to Facebook or Twitter.
To be either "country" or "ghetto" means you gotta learn sacrifice, hard work, long periods of boredom and humility. And in the end, those are things you just don't brag about because you not only don't have the time for it. You don't see the point either......