The "liberal" identity in US is a lossy projection of many different ideology axes to a single one, and is much more closely to just mean "the left" than the definition you meant. I do not believe that they are any more open to new ideas than the right. Both sides stick to the first fancy idea they knew about, and it just happens that those idea are different.

"Liberal" as defined with characteristics in your question is orthogonal to whatever "liberal" is in US politics. And if you ignore children, I think it would be a rather small percentage of human.