Has any us president ever bowed to a foreign leader?

First, while this is a Republican talking point, there is little truth to it. There are actual news photos online of George W. Bush bowing to the King of Saudi Arabia, and also kissing him on the cheek. And Mr. Obama has also bowed his head in front of a world leader whose custom was not to shake hands. When you are a head of state, you are expected to understand the customs and beliefs of other countries. So, yes, both Mr. Bush and Mr. Obama have bowed their head in front of certain kings. This is not an unusual thing to do, and does not mean you are worshiping that person-- it is simply a sign of respect.