Traditionally concrete really wasn't that much stronger without rebar and is much more dangerous if something does collapse.

Wood use to be much cheaper because it requires special knowledge to create strong concrete.

The wooden walls also allow for pipes and utilities to be easily ran. How do you run utilities into concrete homes? The ones I've seen are either exposed or behind a wooden wall.

The US has a large amount of brick homes, but it's usually wooden walls on the insides so it ends up costing more.

It's also more difficult to make a concrete block home look good, and since there aren't too many major storms in many parts of the US, cheap wooden homes work fine.

http://en.wikipedia.org/wiki/Great_Fire_of_London might also be a reason why Europe prefers concrete to wood.