It's not different, or rather it doesn't produce meaningfully different outcomes. I'm not aware of any parliamentary system with a wonderful diversity of thought and a long record of positive accomplishments. You end up with ruling coalitions which are typically pretty awful.
Ironically, America has one of the most open political systems. You register as one party or the other and vote in primaries. This has lead to a huge variety of people replacing hated mainstream politicians. That's way more than you can say for many other countries.
>it doesn't produce meaningfully different outcomes
It absolutely produces different outcomes than a two party system. Smaller parties make demands as a condition for joining any coalition (or similar arrangement). For example, Canada's NDP only agreed to back the Liberal Government on condition of state funded dental care for children being implemented. Now it is. Millions are affected. Whether you agree with it or not - that is unquestionably a "meaningfully different outcome". Other examples abound if you care to look.
>I'm not aware of any parliamentary system with a wonderful diversity of thought and a long record of positive accomplishments.
That's an impossibly high bar. The standard we're talking about is whether it's better than a two party system.
> It absolutely produces different outcomes than a two party system. Smaller parties make demands as a condition for joining any coalition (or similar arrangement). For example, Canada's NDP only agreed to back the Liberal Government on condition of state funded dental care for children being implemented. Now it is. Millions are affected. Whether you agree with it or not - that is unquestionably a "meaningfully different outcome". Other examples abound if you care to look.
You think logrolling doesn't happen in the American system? Parties are made up of factions who will entertain each other's preferred priorities, which is the exact same thing you're describing except that the parties of the various factions are nominally the same. There's no real natural or obvious philosophical reason why your position on gun ownership should imply a position on environmental regulation, religion, infrastructure buildings, racial politics, abortion, tax policy, and more. We're so used to the groupings that they seem natural but if we go back and looking at older American party systems you'll see parties that don't 100% map onto the contemporary ones, with a blend of some elements we would think of as fitting and others we wouldn't.
It's unquestionably a different dynamic. If the party is in power, then the party is in power. Period. They have less incentive to listen to smaller factions. Do they? I sure hope so. But it's not the same.
Furthermore, these internal deals are more likely to be kept private since theres no benefit to airing everything to the press, the public and the opposition.
In a multi-party system almost all those deals are public. Thus, voters can decide if everyone lived up to their promise.
Anecdotally, a recurring theme in conversations I've had while living abroad is the desire to prune or consolidate some parties.
While both sides in the US have big tents, they are effective in whipping votes when things need to get done.
It also helps that detracting coalition partners can't torpedo their leadership. Historically, factions within a party, like Blue dog dems or Tea partiers, had to wait for an election to litigate their grievances.
Well, yes, this was where I was going. The coalition is just formed before the election takes place. I live in a city with "nonpartisan" elections and I feel like it mostly just makes it difficult to understand what candidates in local elections even stand for.
Ironically, America has one of the most open political systems. You register as one party or the other and vote in primaries. This has lead to a huge variety of people replacing hated mainstream politicians. That's way more than you can say for many other countries.