I mean the dimishment of the individual for the potential* betterment of society as a whole or advancement of some ideology. In this post I will try to clarify the differences between the US's incumbent system of individuality versus the rest of the world's collectivism.

But first, back to specifics. It is not controversial to say you have to give up many individual rights by living within city limits. My example above was the lack of property rights when living in a large city like San Francisco. You can't do with your property what you like because the city values social harmony over individual volition and rights. They effectively own your property and allow you to do some subset of things on their whim. Another example of this is city wide smoking bans in privately owned businesses and property. Depending on your point of view this may be an entirely worthwhile thing if it betters society as a whole. But it is definitely the diminishment of the individual. It is a restriction of their behavior despite no use of force or fraud.

More generally, there are two takes on freedom as implemented by governments. The first is that of negative liberty as originated by Kant and fleshed out and implemented in foreign and domestic policy by Isaiah Berlin and his contemporaries in the US federal government in the 1950s-1980s. It is the idea that freedom is the absence of obstacles, barriers or constraints imposed by external agents. In it individuals are free to the extent that they are not interfered with in their personal choices or behaviors. This fits snugly with the US founding documents like the declaration of independence and the bill of rights. US citizens have generally been free to do whatever they want as long as they are not hurting our defrauding others. I will not try to convince you this has existed for most of the past because it is incredibly obvious and the very heart of the country's founding ideology.

Almost all other countries take a different approach. They believe that individuals do not really have full volition and that often internal things restrict their freedom just as much as external things. Like the smoking example above, no one is forced to go to a resteraunt that allows smoking. But in a collectivist point of view people that do go aren't really in control of themselves and need to have their behavior restricted for the greater statistical good. The individual's volition is not valued nearly as high as that of social harmony and so force is used to constrain their behavior. This is positive liberty. It is not inherently bad but it often leads to troubles with authoritarianism due to the concentration of power and acceptance of the use of force to interference with individual choices. This is bad and often has lead to very bad things happening.

Even if you value social harmony over individual choice the slow shift of the balance towards positive liberty in urban areas of the USA is bad if only because the USA is the last nation left that prioritizes the individual choice over social harmony. If wiped out here it the world becomes a much less diverse and free place.

*, potential: And this is another key point. In political systems that value social harmony first decisions are made based on potential future outcomes. This leads to things like future crime wherein certain behaviors that don't hurt or defraud others are met with violence by the police because there's a statistical chance the person involved may do something bad later. The epitome of this is drug laws but it also applies more generally.