Very, very odd "reasoning."
If I commit a crime, murder or otherwise, in the USA but flee to a foreign country, I can indeed be indicted for the crime. However, I believe I would have to be physically returned to the USA to be tried. So I'm not sure what your point might be.
If I wage war on the United States I would expect them to return the favor, particularly if I'm overseas and in a location not amenable to arrest and extradition. This presents obvious problems with definitions and designation, but I find nowhere in the Constitution that a US citizen engaged in warfare on the USA has special privileges requiring him to be arrested and tried, rather than killed in the same way as a non-citizen engaged in the same activities.
IOW, if I'm in Afghanistan shooting at US soldiers, I expect them to respond in exactly the same way as if I'm an Afghan shooting at them.
Why would you have to be returned to the USA. You claimed that the Constitution does not extend beyond the shores of our nation.
Why can't Obama send a drone out to blow you and your sailboat up as you flee in international waters from a murder rap wherein you killed Nancy Pelosi? I mean if as you say your Constitutional Protections end at the border...