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.