No, it wasn't.
Partisan polarization may have been, but only because the divide between the major parties didn't capture the major salient ideological divisions in the country, so that the polarization that existed didn't align with partisan identity.
This had nothing to do with TV regulation (and, indeed, predates TV), and everything to do with the long period of partisan realignment between the New Deal and the mid-1990s.
Cynically speaking, if you are able to control the narrative it stands to reason that there would be less polarization simply because you are manipulating what the public is being told.
"The smart way to keep people passive and obedient is to strictly limit the spectrum of acceptable opinion, but allow very lively debate within that spectrum...." ― Noam Chomsky, The Common Good
So if we see regulation, especially content regulation, polarization is likely to increase as long as not every dissident gets banned.
These wars stopped with social media. They can't possibly happen if everybody has a voice and can call BS when they see it.
If you start to regulate media this way, you will destroy this and we will tumble head-in to yet another war.
Administrations used to hiding bad failures can no longer do so.
You can't have another Nayirah testimony if everybody is gonna point out what a lie it all is online.