The same insurance company can set up in multiple states now, can’t they? What does “selling across state lines” really mean? It might mean that the insurance policies can bypass state regulations by setting up shop in the most lenient state and selling nationwide from there. It’s debatable whether letting states lose control over their own regulatory structure like that is a conservative position or not.
It is debatable, and that state/Federal conflict is unavoidable once the Federal Government gets involved in healthcare, as it has been for many years.