So I repeat my earlier question - what is the point of having a president in a constitutional democracy when he appears to be able to exercise powers not available to a monarch in this country since the time of King John?
You appear to have a serious misunderstanding of how the US federal government is organized. The US has three separate branches of government. The Legislative Branch (Congress) is tasked with writing the laws of the land (and with controlling the purse strings.) The Judicial Branch is tasked with adjudicating/interpreting those laws. And the Executive Branch is tasked with executing/enforcing those laws. And "
the point" of this structure is to limit the power of any one branch and enable any one branch to "check" the powers of the other two.
The current British Monarch is only the Head of State, a figure head position with essentially no power. The US President is Head of State AND Head of Government AND Commander in Chief. So yeah, POTUS has considerably more power than the current British Monarch. But the British Head of Government, the Prime Minister, has far far more power than POTUS because the PM heads the legislative branch, the executive branch AND the treasury, and Britain has no judicial branch.
As for the King John comparison, I challenge that. King George, who lived centuries after John, had far greater power than POTUS ever had, which excess of power resulted in a certain rebellion in the late 18th century.