In order for CNN to turn into BBC CNN would have to fire everyone (management, staff, reporters, personalities), increase investment in actual reporting by about 1000X, and somehow find a staff of competent people to work for them, which would probably be hard to do in the U.S.
CNN is basically a very well funded high school "journalism" workshop. There product is garbage. It is embarrassing beyond belief.
The best cable news shows in the U.S. are The Daily Show and The Colbert Report. The best real news program is Democracy Now. (Judging these things in terms of critical analysis, original reporting, coverage of uncovered stories, the people interviewed, seriousness of topics covered, etc.)
The only bias CNN has is towards incompetence and stupidity. Just about every news outlet in the U.S. has the same bias.
Bias is an irrelevant issue. All political parties and politicians are continually lying and attempting to mislead the public. Any competent news organization will always be "biased" against some political party or another if it is focused on the truth.
A good news organization maintains its bias for truth regardless of the subject of coverage. Even when a news organization fails in this respect, and exercises its bias for truth with only some subjects, it can still be useful. Once a news organisation abandons the bias for truth entirely, or is simply made up of people too incompetent to discern truth from fiction, then it is totally useless.
That is the bulk of the U.S. media.