So what does Iowa have to do to meet your standards? It will work out in the end as they will probably play Ohio State in the Big Ten Championship, but that's totally false to say it's clear they're not as good as a one loss team. When somebody beats them, yeah they'll drop way lower than the other one loss teams, but that hasn't happened.
As for Carolina, why does Alabama get a pass for losing to Ole Miss but UNC just lost to South Carolina because they're no good? The only argument I've heard about the Alabama/Ole Miss game was that Alabama turned the ball over, lucky play by Ole Miss, one time deal type of thing. But Carolina plays the worst they've played in years and loses to South Carolina and now they're just not that good. I will give you Carolina has beaten some really pedestrian teams though, including 2 FCS teams. That has nothing to do though with Tennessee not being a very good team.
Carolina and Alabama both have one loss because they are beatable. They also only have one loss because they're really good teams. But let's say Iowa remains undefeated, then upsets Ohio State in the Big Ten Championship. How could you possibly say Alabama is still better than them? I know that's a stretch, but if you want to look at resumes, which is basically the criteria, a loss on your resume is already less impressive than winning every game.