The US Congress has, by standards of other Parliamentary bodies, weak party discipline. The parties in the Australia&#x27;s Parliament exercise almost totally complete voting discipline (formally or informally). The UK somewhere in-between with the concept of the three-line whip.<p>In that sense the USA already has a coalition party structure: various voting blocs form within the two parties and occasionally defect against the rest. In Australia we call them &quot;factions&quot;, but their role is to seize control of the party and then enjoy the fruits of party in discipline. In the USA they can instead directly exercise their votes on the floor of Congress.<p>This is partly a consequence of the ability to mix appropriations with other bills and for amendments to happen in committee. In Australia neither of these is possible: appropriations bills can <i>only</i> deal with appropriations or they become totally invalidated, and amendments have to be moved in the open. Party discipline becomes necessary under such conditions, but the <i>Parliament</i> as an institution is arguably more functional.<p>Another cause is the primaries system. Members of Congress are answerable firstly to a constituency that represents outliers of outliers, not to the general electorate. They are motivated to occasionally defect.<p>In any case, even if you introduce multi-member electorates, gerrymandering doesn&#x27;t vanish. And the USA needs a number of other electoral reforms, too: independent electoral commissioners, replacing first-past-the-post with another counting method and so on.