WASHINGTON – The Supreme Court on Thursday upheld the nationwide tax subsidies under President Barack Obama’s health care overhaul, in a ruling that preserves health insurance for millions of Americans. The justices said in a 6-3 ruling that the subsidies that 8.7 million people currently receive to make insurance affordable do not depend on where they live, under the 2010 health care law. The outcome is the second major victory for Obama in politically charged Supreme Court tests of his most significant domestic achievement. Chief Justice John Roberts again voted with his liberal colleagues in support of the law.