This is related to something I often say: The US is more liberal than Europe.
Much of Europe feels relatively rigid, in the sense that there are ancient attitudes, customs, social structures, and institutions that would seem out of place in the US.
You might say Europe is to the left of the US, but then we'd be talking about something else.
Assuming your premise is correct: What did you expect?
The origin of modern America dates back about 400 years, the origin of Europe about 2000 years. Also, the reason for many early US immigrants was to escape ancient European social structures. Europe was already crowded before America was explored: there simply was less room for outside influence from other parts of the world.
Even so, there are also quite a few attitudes, customs, social structures, and institutions in the US that would seem out of place in (most of) Europe. In fact, the sentence may even hold true for many comparisons within Europe.
I doubt, one could conclude that -- due to such differences -- one country or nation is more liberal then the other.
What matters is the nature of those differences. For example, in one place it's considered acceptable for a government to regularly collect money for a church. In the other, this would look very suspicious.
No offense, but it does not even make sense to talk about Europe like that. Europe consists of lots of different countries, that are very different and often don't even know much about each other.
Though I must admit I have no idea how much of that applies to the US, too.
Much of Europe feels relatively rigid, in the sense that there are ancient attitudes, customs, social structures, and institutions that would seem out of place in the US.
You might say Europe is to the left of the US, but then we'd be talking about something else.