The filibuster forces consensus. It's hard to get a ten vote majority if you're arguing strictly along party lines.

The real problem is that there are just two parties that hate each other to the core. In a multi-party system, parties would be forced to compromise and find agreement with other parties, and this would become normal.

So get rid of congressional districts and instead fill the House according to proportional representation.

You don't need to go that far, just getting rid of gerrymandering (and thus, "safe" seats) would accomplish much the same in terms of forcing candidates to appeal to a broader constituency.

Any kind of district system will still result in a two-party system. You need to get rid of the district system. A district system only represents the majority opinion in each district, so a very large minority of Americans will effectively not be represented. It also pushes people to vote for the "lesser evil" instead of voting their conscience.

The US needs more than two parties.