It is obviously more nuanced than you make it seem. Do you really think it would be constitutional for the government to target a specific religion or race with drone strikes as soon as any of the targeted group were to go on vacation in e.g. the Bahamas? I don't necessarily disagree with your conclusion with regard to the current drone strikes, but I think your rational/analysis is deeply flawed and there certainly isn't a complete trashing of the constitution as soon as a citizen leaves our borders.