Most health insurance in most of the world has the concept of "pre-existing conditions".
How could it be otherwise? Insurance was invented to hedge risk. In the case of healthcare, if you literally already have a condition that has known and ongoing costs associated with it, it doesn't make any sense for an insurance company to insure you against that risk – the risk has already manifested.
No, that's not right. Public health insurance in the EU does not use that concept. Participating insurance companies are not allowed to set rates that way, since it doesn't serve the public good.
Only since the Affordable Care Act (“Obamacare”). Before that, it was common to not be able to get insurance with pre-existing conditions at all without being covered by your employer. And even sometimes your employer’s plan had a waiting period for pre-existing conditions. I got stuck without insurance for a long time after college (being able to stay on your parents’ plan after graduation is also an ACA provision) and still have nightmares about it.
You’re implying the situation is as stable as it is in other first-world countries. It’s not. It’s brand new, and Donald Trump has sworn it’s going away.
With respect to pre-existing conditions, it is equal treatment. I don't know what you mean by stability. I'm just reiterating the current state. Policy in other countries is also contingent on government policy and subject to change. Any alternative would be new too.
How could it be otherwise? Insurance was invented to hedge risk. In the case of healthcare, if you literally already have a condition that has known and ongoing costs associated with it, it doesn't make any sense for an insurance company to insure you against that risk – the risk has already manifested.