Why is Atheism more controversial in America than Europe?

[TheMessiah]

In Europe, Atheism seems....normal, which I don't think is the case for America.

[Cato]

You don't have American Jesus:

[Minimalist]

Too many nutty Southern Baptists.

[Ashground]

Because in Europe religion disapproves of atheism, in the US religion & politicians disapprove. Politics is a field of compromise, practicality and rhetoric. Religion is a field of dogma, superstition and a subconscious terror of displeasing your imaginary friend.
I don't mean this in a condescending way, but I sometimes feel sorry for atheists in the US. Although I know there are far worse places to be an atheist (At least it isn't punishable by law). I've also noticed that American atheists usually seem more aggressive, maybe because they feel constantly on the defensive.
Luck of the draw that I was born in a pretty secular town.

More than 35% of constituents say they do not practice a religion, which is above the national average, according to figures from the ONS 2011 Census for England and Wales. Source

[Homeless Nutter]

It's called: education. And no - home-schooling isn't it.

[Pyrrho]

...
I don't mean this in a condescending way, but I sometimes feel sorry for atheists in the US. Although I know there are far worse places to be an atheist (At least it isn't punishable by law). I've also noticed that American atheists usually seem more aggressive, maybe because they feel constantly on the defensive. ...

Two things.  First, you are right that American atheists often seem more aggressive online.  This is because atheists are regarded as the worst villains possible here, and are, as you say, on the defensive.  (You might suppose it is hyperbole to say that atheists are regarded as the worst villains possible here.  I invite you to research the matter online and see for yourself that I am telling you the truth.)  Second, we feel sorry for ourselves, that we are not in a more civilized country where atheism is the norm.

Until you have lived in a society that is filled with religious crazies trying to shove their religion down everyone's throats, it is probably very difficult to imagine how upsetting it is.  Even if you visited, it would not be the same for you, as you would know that you may go home and be safe.  We are pretty well stuck here.

Obviously, you are right that there are worse places for atheists than the U.S., but that is no comfort to me.  That someone else has it worse does not make me feel better.  I would be happier if everyone else had it better, as I gain nothing from others being worse off.

[Exian]

Do we know this for sure? I mean, Rome is in Europe, wouldn't that be like our South?

[Ashground]

I'm sure the US will eventually grow out of it.
[DELETE LINE]
I hope the US will eventually grow out of it.

Although I doubt - I'm an atheist, it's what I do - that this will happen any time soon.

[robvalue]

I think it's because America was (not) founded on Christian principles.

I too really sympathise. I know I've got it easy, in terms of religious nutters. That's one of the big reasons I wanted to join an atheist community to help provide some relief from the madness.

It's hard to say exactly what the cause is, but I think the point about politics is a very valid one. There's nothing like the kind of preaching and religious bias in our politics. Shit as it is, if anyone started talking about "what God wants" in a campaign speech, they would probably have committed career suicide.

[Foxaèr]

Because the Europeans were smart enough to send all the religious nuts over here back in 1942.