I'm going to write a considered response to this thread for the benefit of others, but OP- you're wrong, there have been issues and/or these countries have made exceptions- e.g. in Ireland you go to prison with people of your own sex (as in if you are MtF you go to prison with men because actually in the end you are viewed as a man in the eyes of the law). But I don't think you actually want to understand anyway.
The biggest, long term problem with society wide self-ID, I think, is statistics. Long term, self ID will harm women, and by that I mean people born with XX chromosomes and the corresponding reproductive biology.
In life, people with XY chromosomes have advantages over people with XX chromosomes and so if they start identifying as women, maybe after they've got their first job, or stated on a career track in STEM, or in their 40s or 50s when they've already achieved success, that will start to skew statistics. People will say the gender pay gap is closing, there are more women in STEM, there are more women on boards, but it will be transpeople skewing those figures. So initiatives to help women may be stopped and it will be women (with XX chromosomes and the burden of reproduction) who lose out.
Also, in crime it will become impossible to distinguish crime committed by MtF trans from the rest of the population. This has huge implications for keeping women safe.
The true, long term impact of Self-ID can't be judged for years.
But it's also lying to say it's not causing problems now.