American parliamentary system with post-1789 divergence from OTL

[mencken]

Suppose I told you that the Speaker of the House was viewed as the most powerful person in American politics today, with the President viewed as a mere figurehead. What points of departure in post-Constitutional Convention history could most plausibly have led to such an outcome?

I think successful impeachment of Andrew Johnson and/or a retconning of the Jackson and (both) Roosevelt presidencies stand out as least unlikely.

[Kingpoleon]

I suspect this would be most likely to happen just after Madison's Presidency at the latest. A powerful chief executive who lead America into a coalition with Napoleonic France successfully would probably cause bad consequences for his successor's powers.

[Skill and Chance]

Make the Socialist Party much stronger in 1912 and have it split the Democrats and take some votes from Teddy Roosevelt as well.  Taft wins reelection in the EC with <30% of the popular vote, possibly while finishing second.  At all other levels, there is a supermajority in congress and the states for progressive reforms and a 2nd constitutional convention is called with the goal of making Taft irrelevant and reforming the EC and congressional representation.

[President Punxsutawney Phil]

I suspect this would be most likely to happen just after Madison's Presidency at the latest. A powerful chief executive who lead America into a coalition with Napoleonic France successfully would probably cause bad consequences for his successor's powers.

Another thing is, this nation was still feeling out its constitutional norms at that time. We where a young democracy. So it's easier for this to happen earlier rather than later, when people had gotten used to the idea of a powerful president.