You don't have to break up the country, you just give more power to the state and local governments.
That doesn't work in a federal system. The central government always grabs more power. In other words, we've already tried what you suggest, and we wound up where we are now. State governments don't have any power because they don't have much funding, and have to get it from the federal government. States can't increase taxes to make up for what they get from the federal government in order to opt out of federal mandates, because their citizens would be taxed too much (having to pay 30% taxes to the IRS + another 35% to the state government isn't going to go over well). Breaking up is the only way.
Lots of small countries leads to all kinds of inefficiencies regarding trade, customs, defense, law enforcement, immigration etc etc.
That's why I never suggested "lots of small countries", only about 5. The present states would still be part of larger federal governments, just smaller ones limited to regions instead of the entire continent. There's no reason for Vermont and New Hampshire and Maine to all be separate countries, for instance. But having them in the same country as Missouri, Alabama, and Idaho just isn't working. Each new nation would have over 60 million people (assuming equal division), which is a good size for a country.
In fact what they are trying to create with enormous amount of trouble and complications, is not very much unlike what we used to have, a weak fed (because of the difficulty of getting 27 sovereign countries to agree to anything)
See, here you're agreeing with me. We tried the confederacy thing ages ago, and it didn't work out well, so we wrote the Constitution instead, and now we have a strong central government that grabs too much power. You can't have it both ways with a big country: either you have a strong central government where no one's happy and you have our current situation, or you have a weak central government where nothing gets done and you have all the "trouble and complications" you refer to.
So, my solution is a compromise: break the country up into smaller units, but not too small.