This whole federation of semi independent states concept, best illustrated originally by the United States is just one way to evolve a world with some seeming common purpose and absent open warfare. It is a clever one that doesn’t claim to cure all social ills or create mutual love of all humanity. Our ‘Founders’ didn’t seek to create a common morality or a perfect union, just a more perfect union, a common defence and promote the general welfare. There was a degree of reliance on our mostly similar heritage as it stood at that time. Unity in pursuit of defence from European imperialist powers was the main goal. It was a very loose compromise which left some huge moral ambiguities unaddressed, most prominent and negligent of course being slavery.
It relied upon majority consensuses at the time, now accepted in some part as greatly, inexcusably flawed, such as regarding gender roles and the sanctity of life to not be important issues compared to pursuit of a common front defined by contiguous geography.
Our founding was a clever, practical cobbled together effort to create a region without open border warfare on a continent with huge wild and slightly human populated frontiers. It worked by kicking down the road some hugely important problems as well as some trivial ones. It allowed us to put off the inequality of treatment by race and gender for decades and centuries and even the founders were aware of the human tragedy of not addressing those issues early in order to secure a union. It allowed individual states to carve out their own cultural and religious identies to avoid the madness of the religious wars and purges that had plagued Europe but also allowed them to perpetuate human rights violations under the guise of religion and culture.
Federation is one way of eliminating state upon state open warfare. Optimally it would allow a common morality to slowly evolve by allowing people to chose which system, culturally defined laws and general attitudes they wished to live under by flowing from one uncontrolled state border to another and the huge issues that have to be addressed such as whether unborn human life trumps the right to control ones own body to eventually be peacefully resolved. Of course the premise that justice delayed is justice denied speaks against peaceful moral evolution and demands immediate undelayed rectification.
Ultimately humanity is growing closer and closer by increased numbers, easier transportation and near instant communications. I think that the Federal compromise is still the best solution although all out sectarian war is another solution. Federalism has the problem of allowing percieved injustice and moral travesty to exist in ever smaller pockets while society decides on consensus by observation and slow evolution. Sectarian war has the PR advantage of stoking the Crusader, let’s right this percieved wrong or die trying.
All that being said, there are different types of Federalism such as the difference between US Federalism and Indian Federalism and Swiss Federaliam. There are possibilities of layered delegated powers vs intermingled concurrent federal powers. Then there is dissolution of the Union altogether and allowing ideas to establish controlled borders and take up arms.
I opt for some variation of Federalism because it is practical and runs less risk of killing vast numbers of us although the righting of moral injustice may be delayed.