Do you realize how many things the government provides for you on a daily basis? You would not be here if it were not for a government. So many jobs that nobody really wants to do are done by the government: the people who keep the water safe, people who keep the streets clean, people who regulate education.
And sure, those tribes can thrive without a government, but that's due to their size. For a country as large as America, a government is necessary to keep everyone in check; there is so much diversity in peoples opinions, practices, and so many possible "immoral" acts that at the end of the day, you'd probably be a murder victim without a government. Good luck living in a world where people can act on any desire, as many people's desires are not necessarily to your benefit.
In a world without a government, there would be a lack of many crucial things. First things first, there would be a major resources deficit, because the government regulates and indirectly provides clean water and safe food.
Due to the lack of fresh water, populations would congregate around natural springs and underground, self-filtering sources. Unless people were able to organize themselves enough to provide a reliable water-cleaning service, those natural springs would deplete almost instantly as water usage rates surpassed the rate at which the sources fill. Imagine an entire town using only one or two small wells.
Okay, so finally we as a population have gotten the water issue sorted out. There are big water "companies" who filter the water for us that aren't affiliated with any higher powers. Great! But what about food? At first, most of the population would attempt to resort to agriculture to support themselves. Unfortunately, artificial pesticides and fertilizer that everyone used to rely on are now no longer good, as there are no more regulations. That means that as far as the common people are concerned, the creators of those products can put whatever they want in their products to make them cheaper and easier to make. Eventually, people would either learn to rely on homemade, natural pesticides and fertilizers or start borrowing from the neighbors. Honestly, most would start to rely on neighbors and a farmers' market system would evolve to provide food for small communities.
We've now got two issues resolved, if even that. We've built their solutions on a very delicate balance that could tip at any point; they could tip at one single error. And in a world of 7 billion+ people, that's bound to happen. This balance is called trust.
With a government, we are able to trust the systems that keep us alive. Without one, we have to rely on the morals of every single person. As a race in general, we can't do that. We have to be united under a common leader to maintain sanity. So by saying anarchy is something you want, you're saying you'd be able to trust every single person on the planet to help keep you, your family, and your friends alive. Because one person can't provide everything they need for themselves; we clearly aren't solitary creatures. Even in the earliest stages of humanity, we lived in groups that everyone helped to maintain.
By requiring certain things and putting forth regulations, a government creates a near infallible trust system. And if we somehow did fall to anarchy, we'd end up creating small groups with a general leader, and before we know it, we'll have a government once again.
