Three Branches

     Oh, that James Madison, how he did worry about the ways in which a government could get out of control:
     "The accumulation of all powers, legislative, executive and judiciary, in the same hands, whether of one, a few, or many, and whether hereditary, self-appointed, or elected, may justly be pronounced the very definition of tyranny."
     You'll find that gem in The Federalist Papers No. 47, in which Madison fisks theories of democratic government as put into practice in some detail, with particular attention to the separation of powers.

     The History Channel has a quicker read on the subject, with only a little handwavium.

     Either way, it's worth a review, especially against the backdrop of a President who claimed to West Point's graduating class, "We won everything.  [...]*  We had a great mandate and it gives us the right to do what we wanna do to make our country great again."

     Presidents do not, in fact, have the right to whatever they want to do, no matter their motive; the powers of the President of the United States, like the powers of our national legislature and of our Federal courts, are circumscribed by our Constitution and each is balanced against the powers of the other two branches.  That's how it works.  Those are the rules, and if you kick over the table, what you are left with is not the United States as created by the American Revolution and codified by our Constitution, but some other thing, an illegitimate and malformed accumulation of powers, "the very definition of tyranny."
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* I left something out: he said, "We won 2,750 districts against 505, 2,750 against 505."  It's a number from thin air.  That's not how Presidential election results are tallied.  Yes, he won both the Electoral College and the popular vote, but this number is neither of them, and the total does not square with the number of counties and their equivalent in the U.S.