It seems to me that the Chile security already DID create an international incident. The SS would be within their right to start dropping Chileans as needed to protect the pres.
My main concern in all of this is that the SS failed to do whatever was necessary to protect the pres. That disturbs me more than the acts of the chileans.
It is disturbing, but if the SS cannot trust the security forces of host countries, the president simply cannot travel. It's that simple.
-T