It would be horrible to live under a non-Catholic state which had an official false religion. A secular state isn't always a picnic, either. The next best thing to a Catholic state is one where,at minimum, natural virtues are regarded and upheld and the Church has rights. That is less likely to happen where there is an official national religion.
We can't live in a perfect world and God hasn't provided or allowed for a Catholic nation to rise in our times, yet. Maybe He will, I hope and pray, but we make do with what we have and trust in His Providence.