Thus if a third party on the right forms it splits the right and the left wins. As the left implements its agenda the right gets scared and outraged. It unites and then wins elections.
If the left gets split the Republicans win. When they implement their agenda the Democrats get scared and outraged... they get back together and win elections.
The system was designed by Democrats and Republicans to perpetuate the Democrat and Republican parties. It is designed to see that all other parties fail. And guess what? It works exactly as designed.
America was designed with the American family in mind. One can take the view that both parties are inherently greedy, selfish, self-centered, certainly. And of course, your post then more functionally expresses that viewpoint -- to wit, that greed is what motivates both parties, and in that venue, are one party, per se.
Let's imagine, for the sake of argument.. a different two party system: Say, Greenies and Constitution Party. Let's suppose each of them offers "real choice". Over time, your same view about Dems and Repubs will be applicable to these two newer parties, IMHO.
Taken in the small, imagine a Republican Husband and a Democrat Wife. Overtime, one will see there are unifying factors -- income, investments, religions.. even tho' politically, they appear different. Are they greedy, then? Are they "one" party to the exclusion to anyone else trying to enter the "race"?