> "Real butter, because margarine is shit"
I agree with your post, I just want to add something to this.
Aside from just choosing between butter and margarine, there are also "spreadable butter" products, which mix butter with vegetable fats, for a spreadable consistency and a better saturated:unsaturated fats ratio. The one I have in my fridge right now tastes exactly like butter, but has ~500kcal per 100g instead of the ~700kcal in pure butter. The only downside is that it melts faster on warm toast.
The ingredients are butter, rapeseed oil, water and salt, so it's not some weird industrial concoction. Do avoid the types with palm oil and such, though. They're less sustainable and I find them to have a slightly garlicky off taste.
We do not need carbs. We can live without any.
That said, the average American diet is imbalanced in favor of carbs, with pretty much everything sweetened. My European diet is a lot more balanced out, we eat brown bread, regular pasta and rice, etc, all part of a balanced diet (can't beat a brown bread, ham and cheese sandwich. Real butter, because margarine is shit)
The other problem the US diet has is portion sizes. American portions are big. As an occasional tourist I can appreciate it, but at the same time it's one reason behind the obesity crisis.
The UK has a similar problem. Compared to where I'm from (NL), eating 'out' is affordable, and you can load up on a full English or a carvery for around 6 pounds. Drinking a ton of beer also seems to be normalized with a big percentage of the population.