George Washington "demanded" nothing of the sort. And the constitution is silent on such an issue.
Washington's Farewell Address was primarily warning the new nation about those designing men who would try and split the Union. It's alleged isolationism was meant for that day NOT today. Then the US had no military or navy capable of getting involved in a European conflict thanks to the Jeffersonians. But Washington's (actually Hamilton) fear was that such an involvement would lead to a CIVIL war here since the Jeffersonians were ready to side with France.
Anyone who reads the Farewell Address cannot honestly claim it was a document supporting Isolationism for all time. Hamilton was FAR too intelligent for such pap.
Anyone who reads it knows that Washington recognized we had international comitments even then, which must be faithfully observed. An address delivered as we were engaged in our first international war, against jihad, far from our shores.
My opinion, most who quote a line or two haven't read it.