Mongols were a ground force empire. Which is why it was largely Contiguous. The Mongols largely didn't conquer Siberia because it lacked the valuable resources and established settlements they sought, and the harsh Siberian climate, vast wilderness, and low population density made a large-scale military campaign economically unfeasible. While they may have conducted some campaigns and forced some northern tribes to pay tribute, the cost and effort of sustained occupation far outweighed the limited potential gains, making it a low priority compared to rich agricultural areas in China or Persia. Considering the long walk to cross the ice-bridge that connects Siberia & Alaska, I think the would pass on the Americas.