I think the difference between the USA and other countries is a different stress of social trends and points of critical mass.
Social trends operate by groups sharing a common idea that makes them feel included. This is a primal instinct that makes us social animals - leads to procreation and species survival, etc. Many may not initially share the idea but change so that they can become included.
In the USA religious belief had a strong starting point around which groups were able to bond. The beliefs are maintained because there is no other opposing strong meme that can reach a critical mass to switch the social trend.
In Europe and the UK, religious beliefs have a much longer history, and even though social bonds were formed around common religious beliefs, I suspect that those beliefs are becoming old, tiresome, and less relevant to modern life, and the critical mass is waning in favor of numerous other reasons to form social groups. In essence religious belief in Europe is losing its adhesive power.
In the USA I detect that the same trend is occurring, but just a few years/decades behind Europe. Polls show some 20% of all Americans are unaffiliated to a religion, but that jumps to some 34% for the under 30 year olds. As the generations age out then those proportions seem likely to increase.
We will know a social critical mass is achieved in the USA when politicians stop claiming their strong belief in God (currently seen as an essential vote winner), to simply avoiding the claim, as is the case in most of Europe (it is a vote loser to be seen as overtly religious). Note that I am sure most US politicians aren't truly particularly religious, and they will readily alter their views if votes are involved.
Religious belief in the USA will flip quickly once we approach a critical mass in a similar way, stronger I suspect, that the LGBT movement has blossomed. As non belief becomes more common then more non-believers will come out and be prepared speak up. And that will be mainly because they will not feel isolated, but instead feel included in a recognized social group.
As I said it all comes down to feeling included and people will be prepared to believe or say whatever is needed to feel part of a group and feel safe.