Success is defined as the achievement of something desired or planned. For America, success was achieved over time, but not within 15 years. America was too big of a nation to make change so easily. There was success in the sense that eventually change occurred; because of the "voice" of the political party that continued to get attention, and there wasn't success in the sense that America was trying to make changes that quickly. America wasn't and was successful at the same time, because it was successful in encouraging change, but unsuccessful in changing quickly.
America could be compared to an enormous ship with definite direction, and one day this ship would like to change its direction, but is unable to do so fast enough because it is just too big. There are many individuals, political groups, powerful business men and others trying to influence and change its direction, to suit their particular interests. They were un able to accomplish this because it is just too large a ship with too much momentum. It is as if all of these parties are pushing with their hands on the ship to try to push it in the direction most suited to their will. The different parties are pushing the ship on different sides and in different directions. The large ship is hard to move off course with much power let alone with different powers pushing in different directions. This in itself is the safety net in a democratic solution for society, it takes much pushing and much work to achieve direction change with the ship. The party platforms continue to voice out their opinion to the public on how America will be better in another direction, and if more and more people continue to push with the party in a certain direction, eventually the ship will begin to slowly turn its direction. This is exactly what happened and over time change occurred. It took a lot of pushing and it took till present to change direction, and the ship will continue to change direction as time goes on over many years, by the influence of many forces.