Leopold Kohr, The Breakdown of Nations, 1957, 1978.
Kohr proposed a breakdown of Europe into smaller chunks, and then federating them together; not unifying them through a central government.
A Europe of Little States: This map shows approximately the genuine component parts of Europe, historically subdividing the great powers, products not of nature but of force. Being all equal in size they are ideally fit to form a successful federation. Thus Europe’s problem – as that of any federation – is one of division, not of union.
E. F. Schumacher, Small Is Beautiful: Economics as if People Mattered, 1973.