OK, I'll try hard not to be obtuse. I understand what you are saying, and the dangers involved to my personal liberty. I still remember a few things I learned from school about what concerned our founding fathers.
If I look at something like this:
http://www.aclu.org/national-security/intelligence-official-acknowledges-policy-allowing-targeted-killings-americans
then all of your arguments make sense to me, and I am shocked and concerned about this admission, and all the things you say, for all the reasons you say, and for the reasons the ACLU identify.
If I understand you correctly, you think the case of Bin Laden is no different, because the real threat to my liberty is that "the people's" role was bypassed and usurped by the government.
You mentioned "checks and balances". If I remember correctly from the 5th grade, this means that no single branch of the government is unchecked, because the other branches have some role or influence, and the people have their roles too, in all the branches.
In the case of Bin Laden, this specific action was approved by both legislative and executive branches of the government. In 2001, in an "Authorization for use of Military Force", Congress recognized that "the President has authority under the Constitution to take action to deter and prevent acts of international terrorism against the United States", and it was "Resolved by the Senate and House of Representatives of the United States of America in Congress" that "the President is authorized to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, ... in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons."
Do dictators require Congressional approval by two houses? Do you think President Obama abused this authorization, because maybe the link to Bin Laden's involvement in the 2001 attacks hasn't been properly established? Do you think the combined government branches usurped my right to play a role in "due process", whatever that means, and this is cause for great concern?
These are honest questions, not rhetorical ones.