So did the ancient Greeks.
Unfortunately, even the most civilized nation can survive only as long as it is militarily able to defeat the armed invader and a well armed citizen militia is no match for the militarly technology, manpower and logistics that a centralized nation state can bring to bear.
The individual Greek city states did fine with their little citizen militia wars amongst themselves and only had to co-operate during extreme emergencies such as the Persian Wars.
Once that relatively uncivilized Romans showed up with the technolgy, manpower and logistics that only a centralized government can field, the independent Greek city state passed into the dust bin of history.
The age old problem is to be able to balance the power of a centralized military with the freedom of decentralized government for civil matters.
The failure to achieve this balance will reult in either a military dictatorship by your own Army (Rome after Caesar) or rule by the foreign Army that has just conquered you (Greece after the Romans Legions arrived).
The Roman Republic tried to address this issue by splitting military power between two Consuls and replacing the Consuls on a regular basis. This, however, led to disaterous military defeats during the Second Punic War as inexperienced Roman Consuls were routinely massacred by the military professional, Hannibal. The long command in the Spanish theater of operations that allowed Scipio Africanus to gain command experience finally allowed Rome to have a military commander with the experience and expertise to deal with Hannibal.
As Rome tried "reforms" to increase the efficiency of it's Army, control of the Army was lost and the Republic perished.
The historical marvel of America is that, so far, it has been able to achieve the delicate balancing act of a powerful centralized military and the freedom of it's citizenry.
If the balancing act does not succeed for future American generations, our progeny will be ruled by either by an American military dictatorship or by a foreign military dictatorship.