Withdrawing the United States from the IMF and World Bank would be “a step backward,” a top U.S. Treasury official said Friday, defending the organizations before a presidential election that could cast uncertainty about America’s future in them. In advance of the institutions’ annual meetings this month, Jay Shambaugh, the undersecretary for international affairs, alluded to a Project 2025 proposal for the U.S. to pull out of the IMF and World Bank if Donald Trump wins.