The US constitution has a really bad early adopter syndrome where it was so good at the time that it's hard to move away from. Nearly every country with a constitution modelled on ours has failed at some point.

"We basically run a coalition government, without the efficiency of a parliamentary system" - Paul Ryan.

To be more specific, our majority-based government locks us into a two-party system where one party just has to be slightly less bad than the other to win a majority. But our two parties are really just a rough assembly of smaller coalitions that are usually at odds with each other.

The presidential democracies that function usually have some sort of "hybrid" model where the legislature has some sort of oversight on the executive office. But they are still much more prone to deadlock or power struggles.

There is no system that is immune to takeover from a demagogue. There's not even any hard evidence that any system is more resilient to it than the US is. It's all just tradeoffs.

Germany had 7 major political parties in the run up to 1933. In fact if you look at the history of dictatorships that took over democracies, having 2 to 3 stable institutionalized parties is actually protective. The other thing that appears to be protective is a history of peaceful transitions of power, which the US has the longest or second longest.

How about we try keeping big money out of politics and using ranked preference voting before we declare democracy obsolete? People have been studying that stuff.

Can you provide examples that support your assertion, that the US system was already generally seen as obsolete in 1926?

Smells like BS.

What is considered the best* system of government? Which country comes closest to the ideal model?

*best is funny to define