No, It's Not Going To Work

When Richard Wolff was asked if we should run progressives as a 3rd party or within the Democratic party, his answer was: both

Maybe letting rich slave owners write the rules for a country wasn't the best idea.

We really need to get rid of the electoral college before we try to a get a 3rd party

Just to correct the beginning - Corbyn's party didn't get 400,000 members, it got 400,000 email signups. The 400,000 figure is just of a mailing list, not party membership - there is no party membership yet and you can expect the membership in the end to be smaller than that, given that you 1. would have to pay for it and 2. would have to quit any party you're already in. I know a lot of people who are Labour members, Lib Dem members and Green party members who signed up for it because they're lefties interested in it, but it doesn't mean they've joined it - they're waiting to see if it turns out decent and viable before leaving their own parties.

Leaving the two-party system behind would take a level of cooperation and foresight that the American public just isn’t capable of, let alone congress.

So if we had a parlementary system we could have kicked Manchin and Sinema out of the party?

Canadian here (also a member of the Steve Boots community, hi!): True coalition governments are exceedingly rare here, federally. A coalition involves the ruling party to be in the minority and incorporate members of another party (or multiple parties) into cabinet positions. What normally happens here in the event of a minority government are supply and confidence agreements, parties work together on an ad hoc basis to get legislature passed with amendments without the inclusion of other parties' members in cabinet. A true coalition was how Tommy Douglas of the NDP managed to get social healthcare passed. More recently, the NDP worked with Justin Trudeau's Liberals to expand healthcare to also include dental coverage without a coalition.

Ranked Choice voting could solve a lot of this

This youtube title seems like its targeted against my recent decision to grow a mustache. ITS NOT DONE YET SAM!

When you have to explain basic civics 90 seconds into the call...