It looks like two totally different countries.
Why was this design considered good?
There are a lot of powers the president has now that the office didn't have a long time ago, and the power of the executive has steadily creeped into everything and grown significantly. If the president were limited only to his powers articulated in the constitution it would be less consequential who the president was. Really, what makes it such a big change is all the executive departments that have regulatory and therefore de facto legislative authority.
We can measure this. The single most basic responsibility of Congress is to pass the budget. Well, how are they doing? When was the last time they were able to pass a normal, annual budget, like they used to do year after year, reliable as clockwork?
If they can't do job 1, they're broken.
So the president rules by executive order, because Congress can't pass bills any more.
The advent of nuclear weapons is one reason.
You need someone to push the button.
Another reason is Nixon, Dick Cheney and many other right of center "intellectuals" have been successfully arguing for decades that the president needs more power.
One characteristic of the US that differs from most other countries is the degree to which the states retain a lot of power to govern themselves, and states will continue doing what they do mostly independently of things at the Federal level.
The way that most Americans talk about the president also overstates the actual power of the office. I half-joked earlier today that most Americans seem to imagine this country as an autocracy in which they get to vote for a new ruler every four years. But it's not. Congress still has more power than the average person-on-the-street seems to realize. Part of what makes Trump taking office tomorrow a bigger deal is that he's also getting both houses of congress for the next two years, which isn't always the case, but we're seeing flashes of congressional Republicans being unwilling give up their powers to him.
Anyway, I also agree with the other answers about nuclear command and control and the dysfunction in congress, especially in terms of congress exercising its power to declare war.
Wikipedia says [0]:
> As of September 2024, the United States Congress has formally declared war 11 times, and has not done so since 1942; 6 of these were WWII declarations. The United States did not declare war during its involvement in Vietnam, although the Gulf of Tonkin Resolution authorized the escalation and use of military force in the Vietnam War without a formal declaration of war. On at least 125 occasions a US president has employed military forces without authorization from Congress. One of the most significant of these occasions was the Korean War, where the United States led a peacekeeping United Nations force to stop North Korea's invasion against South Korea. The conflict resulted in over 142,000 American casualties (about 40,000 deaths and over 100,000 injuries).
And courts can be packed, at times rewriting the Constitution. It's also my opinion that congre$$ has deliberately deadlocked for decades to prevent social legislation and wealth taxes, hence the obscene distribution of wealth, using the voter frustration they created to propel/maintain their seats, since "It's always the other guy's fault" in politics. With perpetual deadlock, the executive branch fills the vacuum.
Previously you had a mentally unfit president with decisions made by VP/Jill Biden/The Cabinet/Bureaucrats/Who Knows?
if there is no one person in charge, there is no people in charge.