America pretended to have checks and balances. Everyone just turned a blind eye to the massive holes in them and pretended things were going to be fiiiiine.
"The dignity and stability of government in all its branches, the morals of the people, and every blessing of society depend so much upon an upright and skillful administration of justice, that the judicial power ought to be distinct from both the legislative and executive, and independent upon both, that so it may be a check upon both, as both..."
— John Adams
And our government doesn't have that necessary firebreak. Justice is part of the Executive.
Source: https://www.mass.gov/guides/john-adams-architect-of-american...
I agree to this Constitution with all its faults, if they are such; because I think a general Government necessary for us, and there is no form of Government but what may be a blessing to the people if well administered, and believe farther that this is likely to be well administered for a course of years, and can only end in Despotism, as other forms have done before it, when the people shall become so corrupted as to need despotic Government, being incapable of any other.