The American electorate - and the rest of the world - is bemused by the dual role of head of government and head of state laid on the shoulders of the American president. Get rid of it. Have a Prime Minister who is a member of, and leader of, the majority in the House of Representatives; most other states do, with the exception of Iraq.
Because the president, senators and representatives all sit for terms of differing lengths, the president cannot plan for the future. Make electoral terms for president, senators and representatives co-terminous and of the same length. Let the Prime Minister pick his cabinet from the majority in Congress like every self-respecting leader in the Western world. Goodbye to the time-consuming coaxing and cosying between secretaries of state and Congress.
A few reforms would breathe new life into the American political scene and lift voting participation above its present abysmal level. Manifestos would mean something. There might even be an end to the duopoly of the two dinosaur parties.
Governments would be accountable and Congress could easily get rid of any PM - or his government - by a vote of confidence. The clumsy, shameful and time-wasting process of impeachment would become a piece of 18th-century archeology. I recommend a shufti at the constitution of the Bundesrepublik.