Ken V - you are quite correct, I dont really understand the US system of government which is why I have quite often asked serious questions about it on here. My remarks about "acting like a king" were prompted by a US acquaintance seriously asking me whether it was correct that The Queen ruled the United Kingdom (she probably said England but I'll let that pass) and that we all had to do what she said!
My serious question in this instance was the news that the President had apparently enacted a law concerning the status of immigrants that was opposed to the wishes of the majority in both the Senate and Congress. It appeared that in spite of the checks and balances which you explain in your post, in this instance the President was able to act as a de facto dictator and there was nothing the legislature could do about it.
So tell me, in spite of all these checks and balances, if Obama says (for example) that from tomorrow everybody has to paint their face bright blue, will you all be walking about blue-faced next week?
(Oh ok, I'll give you George III, btw, - but he was a nutcase!)