If you squint at Devo-Max in bad light, it looks a lot like something familiar to those of us here in the States... Not that we haven't had our own problems with it.
A hundred and fifty years ago, six hundred thousand Americsns died sorting out the primacy of the Federal government over the several States. That notwithstanding, the several States still enjoy a fair degree of autonomy. That autonomy is what prevents such a referendum from becoming an issue over here. Paradoxically, autonomy undergirds unity.
It has several other advantages.
I've heard Federalism described as "fifty laboratories of democracy." It's not a bad image. Each state tackles issues in its own way, some successfully, some less so. The bad ideas get left behind. The good ones -- a key example being the Massachusetts health care reform law that became the basis for the Affirdable Care Act -- become more widely adopted. We are seeing it happen in marriage law, too. And in marijuana legislation. A few States try something new, others see it work -- well OR poorly -- and take the lessons to heart.
And sometimes, different conditions will perforce lead to different laws. Montana, with cities separated by miles upon miles of a whole bunch of nothing, will NEED different highway rules than Rhode Island. It's lunacy to force identical rules on both.
And, last but certainly not least, our founding documents state clearly that a government's legitimacy rests upon the consent of the governed. As a practical matter, it's easier to secure that consent at the local level, than at the State or Federal level. The more decisions that are made closer to the citizen, the better. You feel more like you have a real stake, more like you can have a real effect on policy.
I have a lot of friends who disagree. I expect I'll be hearing from a few shortly. Nonetheless, I'm still a Federalist.