If the Supreme Court in King v. Burwell strikes down subsidies to the buyers of health insurance on the federal exchange, President Obama will call on Congress to change the law to allow the subsidies. There also will be enormous pressure on elected officials to establish state exchanges in the 34 states that don’t have them. Instead, congressional Republicans should be laying the groundwork for market-friendly health reforms and devolving power to the states, meanwhile helping Americans who have difficulty purchasing coverage…