Yes, and plenty of wealthy countries have the same problem, including Australia. As animals it's hard to control yourself because scarcity used to be the inhibitor. You need will power to ignore the initial hunger pains which no one teaches.
> American food is generally unhealthy
Yes, companies like Coke market addictive products like sugar mixed with caffeine and are allowed to hook people. Where is the FDA on that? It's the same FDA that allowed the opioid crisis so I assume they are complicit.
> Food waste - excessive portion sizes lead to partial consumption which leads to food waste
Not really a problem, we ship tons of grain and non spoilables overseas due to our massive agriculture industry. Certain foods can't really be distributed like that. Eating a large portion isn't really a bad thing as it's becoming clear that fasting in between a large meal is better than multiple small ones.
> Excessive portion sizes lead to the need for horrible US agriculture practices because its the only way you can make large portion sizes remotely viable
We actually pioneered agriculture and saved many people from starvation. We've learned from the dust bowl proper techniques to not deplete the top soil and to use circular fields and cycle crops. We've provided these techniques to Japan and other countries and the excess food from our crops goes to Africa.