They are both legal products of consumption and the government trying to regulate their consumable size...
Quite. I can certainly see why people get annoyed by the nanny state.
On the other hand , as a Brit who did an assignment in Houston TX for a couple of years, I was appalled by the large numbers of grotesquely, disgustingly, fat people. You practically never see people completely out of control of their bodies like this in Europe. And I do suspect that the soft drink culture has a lot to answer for. I remember how everything in the US seemed to taste sweet to a European palate. Bread was sweet, potato crisps were sweet, even the jam was too sweet to eat. Worst of all, it was culturally normal for people to drink sweetened soft drinks with their food. (I recall a US colleague being appalled to find there were no soft drinks machines in our office in London. People looked blank and said well you can get tea and coffee. What's the problem?)
I suspect that this has created, in the palates of Americans, a constant background of sweetness, so that foods need more sugar in order to taste "normal". You get the same thing with people who habitually use a lot of salt on their food. Everything has to be saltier, just to cut through what the taste buds have got used to.
I therefore suspect that the way to control the obesity epidemic in the USA is to cut back the huge cultural influence of the soft drink corporations, who have made the abundance and ubiquity of soft drinks into a cultural symbol of plenty.
So, regrettably, borrowing techniques from how we have learnt to control the tobacco corporations may be the only way to do it, cherished freedoms to get appallingly fat notwithstanding.