By David Lawder WASHINGTON (Reuters) – U.S. President Joe Biden will nominate Jay Shambaugh, a George Washington University professor and former Obama administration economic adviser, as the U.S. Treasury’s next undersecretary for international affairs, the White House said on Friday. Biden also will nominate William Duncan as ambassador to El Salvador and Lesslie Viguerie as ambassador to the Kyrgyz Republic, the White House said. Both are career Foreign Service officers. If confirmed by the U.S. Senate, Shambaugh, an expert in international monetary and exchange rate policy, will fill a long…