"My personal feeling is that between 1900 and say now, Americans are more willing to reject the reasoning that gave it freedom to accept the reasoning that will take it away."

I can give several counterexamples to that claim.

Racial segregation "ended" in the United States in 1964. I would claim the country was - at least from a legislative standpoint - more free after than before it. So starting from 1900 I would claim there is a trend towards more freedom.

https://en.wikipedia.org/wiki/Civil_Rights_Act_of_1964

The recent years have seen the acceptance of more people as they are. Gay marriages are now legal which I think is a fantastic achievement in the history of human rights - no matter how long it took to get there

https://en.wikipedia.org/wiki/Same-sex_marriage_in_the_Unite...

So, at least from the point of view of several minorities, United States seems to be more free now than ever. I don't know what the totality of the situation is, though (not an american).