I concur; less is more: Be advised that the expression “United States of Europa” 1) not necessarily will become the official name of the union, it might as well be The European Federation (short form: Europe), or quite simply a continuation of the European Union (the US calls itself a ‘union’, ‘nation’ etc, but rarely if ever a federation. 2) “the United States of Europe” runs a risk of inherently being compared to/regarded by citizens as a “copy” of the USA. Which, if I may say i diplomatically, will make a lot of them misunderstand this initiative: Which is to make a BETTER and more modern Constitution than America’s — and crucially; our member states are not to become like the single states in the US: Quite the opposite; a major point in Europe will be to retain state soverignty in matters that are not specifically placed at the federal level, which will be areas where only supranational governance of common problems/interests require.
Why not something simpler like “We, citizens of Europe…” (which countries etc. can be specified outside the Peramble.