It may be we have always been a nation of liars. Here's a quote from a 1975 interview with Gore Vidal from OUI magazine:

"Black ink begins to fill the atmosphere once you get anywhere near the truth with any American as he tries to hide what he's really doing, which is usually stealing your watch. Ditto the politicians--in spades." I was only almost nineteen then and didn't understand why he said that then. Now--oh, God, do I ever get it!!