I'm still waiting for you to tell us why "things end badly" for those countries that have a State Religion ?
If you don't know, you are allowed to say so, but it just makes a nonsense of your statement if you can't justify it...
In the meantime...
You view is simplistic in the extreme.
(Please note - when I say "The Church" I refer to the C of E)
The C of E remains embedded in several areas of English Law.
Church Property and Ecclesiastical Assets.
Parish Churches, Cathedrals and other Ecclesiastical buildings aren't private properties belonging to a voluntary association. Many exist under ancient trusts or legal arrangements pertaining to the Church's historical status as a National Institution.So disestablishment would raise complex legal questions regarding the ownership, governance and maintenance of these historic buildings.
Ancient Parochial Rights of English Citizens.
Everyone belong to a Parish which confers certain legal rights - such as being married in the Parish Church and the right to be buried in the Parish Churchyard.
Removing establishment would require substantial revision to marriage law and other aspects of Civil Legislation developed around the Parish System.
The C of E also care for about 16,000 Church Buildings, many of them protected historical structures. The preservation of these buildings depends on a complex framework involving ecclesiastical governance, heritage protection, and charitable structures. Disestablishment would require reconsideration as to how this national patrimony is maintained.
A striking asymetry is forming - the historic Christian framework of the constitution is being increasingly questioned as an anachronism while new mechanisms for protecting another religious identity are being constructed within public policy.
The lesson of recent elections is that religion has not vanished from the public arena but has begun to reappear through identity based political mobilisation.
The Anglican Church in Wales is not an established church. Neither is the Anglican Church in Scotland. It would be complicated legally to unpick church and state in England but if that happened then Anglican churches in the UK would still continue.
There is no state funding for churches, so no difference in the stress of trying to find £100k for a new roof with grant making bodies refusing to consider funding religious buildings.