One thing that fascinates me is the blind spot for political parties.
There were parties in the UK by the time of the revolution. By the 1790s there were warnings being emitted about their potential toxicity in the US. But there's nothing done to formally recognize political parties or manage their risk
I always theorized the two-party system on a national level was less a function of first-past-the-post and more a function of a presidential, rather than prime-ministerial system. You need a political machine capable of running a national campaign, and the ones that are big enough to do that will also likely conquer down-ballot elections.
If you no longer have to run a national campaign, you'd end up with primarily state-level parties. The California Democrats and the Illinois Democrats would have about as much in common as the current US and German Green parties. Each state may have two main parties due to FPTP still, but they'd likely be less coordinated and financially linked, forced to form blocs and consensuses at the federal level.
I don't think I follow the argument about presidents vs. prime ministers. Empirically, the UK does have a strong two-party system, so to the extent that they're a comparable case (i.e. setting aside minor things like the history leading to SNP and Sinn Fein), that's a point against your argument.
In the US, we do in fact have parties that are dramatically different across state lines at the state level. This is changing a bit in the last few years, but it used to be only at the national level that the parties were internally homogenous. And even in Congress, except on the hot-button issues, there is some diversity across delegations from different states. Elizabeth Warren and Doug Jones are not the same.
The problem is, if you go to a prime minister (e.g., if Speaker of the House got the powers of the President), then the individual state elections effectively become the national election. Imagine that there are no parties, but you and your friends have a few billion dollars to throw around, and want to make sure that the Prime Speaker is Nancy Pelosi. You'll do that by supporting politicians who would vote for her (donating, but also organizing get-out-the-vote drives, etc. - campaign finance laws can't prevent this). If anyone new wants to enter politics, they'll want to take advantage of your machine, which means that if they're on the fence about a policy they'll default to agreeing with you to make sure you pick them, and oops now you've reinvented parties. It's just an inevitable consequence of two facts put together: (1) FPTP voting, and (2) campaign organization having economies of scale, both in terms of money and in terms of voter attention span.
There were parties in the UK by the time of the revolution. By the 1790s there were warnings being emitted about their potential toxicity in the US. But there's nothing done to formally recognize political parties or manage their risk
I always theorized the two-party system on a national level was less a function of first-past-the-post and more a function of a presidential, rather than prime-ministerial system. You need a political machine capable of running a national campaign, and the ones that are big enough to do that will also likely conquer down-ballot elections.
If you no longer have to run a national campaign, you'd end up with primarily state-level parties. The California Democrats and the Illinois Democrats would have about as much in common as the current US and German Green parties. Each state may have two main parties due to FPTP still, but they'd likely be less coordinated and financially linked, forced to form blocs and consensuses at the federal level.