Surely a federal nation is one where the individual states wish to express unity, but retain their independence in most matters relating to internal affairs. There is of course the necessity to recognise that the federal government will have the powers to decide on various overarching matters (defence, welfare, fiscal policy, etc) but only insofar as it bears on matters that affect all states jointly. To function, a system of state dependent collective governance is required and the states must have the power to offset decisions made by central government which is itself democratically elected This is all present in the USA, but even so it functions far from perfectly. The USA started small with just a few states opting for a federal system as a means of self preservation and as the states developed to the west & south into what they considered vacant land. Conversion from a territory to statehood was considered a great prize, as anyone who has seen Oklahoma will understand. Even so many states have at various times declared a desire to "Secede from the union" over some issue or another,
The EU consists of nation states with several millennia of traditions of independence behind them. When the EU was created only the creators knew that any more than a trading bloc was envisaged. It took many years of gradual tweaking behind the scenes and encouragement of fifth columns and dubious, mis-sold treaties to create a body that clearly wishes to subsume the history and cultures of its members into a bloc only paying scant attention to representation by democratic means, but creating an unelected leadership open only to ex national leaders who cooperate with the ethos and means of the central authoritarian state control. The member states, beyond trade have little, if any commonality of purpose, some have intense dislike for others. This is not federalism.
The Russian system was fundamentally a Communist party dictatorship with more in common with the EU than the USA.
It has been suggested that the UK could function as a federation, but as in the EU the disparity of wealth and population numbers would discriminate against equality in the wider sense.
Mike.X