With the chance of a U.S. default in a matter of weeks, U.S. Treasury Secretary Janet Yellen warned that if the debt ceiling is not lifted, it could trigger a "constitutional crisis." "It's Congress's job to do this. If they fail to do it, we will have an economic and financial catastrophe that will be of our own making," Yellen told ABC on Sunday. "And we should not get to the point where we need to consider whether the…