An island is a natural union of land (and waters) surrounded by oceans (and some concurrent world powers).
Unification of states are only useful for one or several of their minority nations and governments, not so with island states. Their unification advantages the majority of its souls and communities.
For example Ireland is surrounded by the Atlantic Ocean and the Irish Sea and the very competitive world powers Britannia, America and Europea!
Many years I supported the Deutschlander Union because my family was divided betweeen the two Deutschland states. But unlike the Christian Democrats and other nationals i had no advantage of their reunion, instead the clan became even more divided! I would have no further advantage of the European Union too.