Credit Simpson for at least being sincere in her musical offering. There is a semblance of country here (more so than some of the music being released by such "country" acts as Rascal Flatts, for example) thanks probably to producers John Shanks and Brett James in the instrumentation, but "Come On Over" isn't going to make many year-end lists for the best country releases.
Simpson is the only latest act to try and break into the country end. Jewel did so only a few months ago with her debut having middling success so far. Hootie & The Blowfish's lead singer Darius Rucker has enjoyed the greatest impact of the recent converts with his single Don't Think I Don't Think About It topping the charts. This seems to be part of a growing trend as Bon Jovi can tell you with the success of their number 1 hit Who Says You Can't Go Home from 2006 with Sugarland's Jennifer Nettles helping out. Despite the hit, what had originally been billed as a country-based album sure wasn't marketed that way ultimately by the label.
Of course, it is not easy at any level to gain a foothold on the charts and generate CD sales. It's hard enough for those quality singers who are doing country music full-time (Ashton Shepherd, Sarah Buxton, for example), let alone those who have made a name for themselves in other musical genres and try their hand at country. Part of the problem for the outsiders is that all important country radio generally seems to be at least a bit wary of singers like Simpson. (She also probably hasn't helped herself with her dumb blonde affect and getting into a spat with Carrie Underwood over Dallas Cowboys' quarterback Tony Romo and the like). For those who are able to break through, congrats to them.
We'll figure out real quick just how serious and sincere these artists are about country music. If it's one and done album-wise, then we know that the release of country music was really an attempt to cash in on the pop leanings of country instead of making a full-fledged, long-term commitment. Of course, many country acts have gone the other way - starting off as being more traditional and then forging a pop sound that registers as barely country.
To singers and bands whether new to the genre or already been there, to thine own self be true.