We need, and have, a mostly centralized system of government underpinning, agreed upon law system, economics (largely), science, knowledge, etc. Generally, that allows us to operate very autonomously and in a decentralized way already. I seldom see, visit, or interact with the Federal, State, or even local government. I usually interact with regulations only as constraints on my decisions and others. Besides paying taxes and benefiting from fixed roads, limits to hazards, etc., I feel very decentralized and self-controlled most of the time. You're arguing that disassembling that centralized / decentralized system into something more purely decentralized would be better. I don't see it.
first, you state that you rarely interact with distinctly Federal(centralized) entities. ok, i agree :) second, you state that these centralized norms "allows us to operate very autonomously and in a decentralized way already". ok. then, "Besides paying taxes and benefiting from fixed roads, limits to hazards, etc., I feel very decentralized". you're speaking to shared infrastructure. again, this is not a uniquely centralized capability. in fact, decentralized infrastructure is more robust! understand that decentralized consensus can lead to global coordination. not only that, but this global coordination is resistant to singular abuse! e.g. these patterns are resilient. it follows that the benefits you don't see in decentralized structures are actually the end to which you aim and strive for!
Efficiency. Trying to create, maintain, and evolve many, many decentralized systems at the pace our centralized legal / information / economic / medicine / scientific / safety / defense system operates would be far less efficient than the system we have now.
efficiency used to be an adequate excuse. this is why i say that communication is the key to modern decentralization. we aren't there yet: but to yield to defeat before we've fought the fight is to succumb to despair. don't do it; we're human, after all :) best regards.