I think the most important thing to consider here is communication. Often it can be difficult to speak with foreigners in common terms.
I think that different culture might self-select US developers the same way top schools produce highly motivated, successful people because they recruit highly motivated, successful kids. Not to say every US developer wants to climb to the top of some technical or economic mountain, but it seems like maybe there's a smudge more passion among US developers. Also, intelligent, math oriented individuals have other avenues in the US, like finance, (and unlike the rest of the world) dentistry and medicine are lucrative careers. Meaning you choose programming more because you want to program, but in other countries it's because it's a better paying job.
I've also noticed that in some countries, once you've done a few years writing code, you quickly want to join management ranks and develop a coding allergy. More so than in the US, where it seems like 50 year old developers still want to write code. I get the sense that, in some countries, if you don't get into management then you are a failure at some level. So in the US you can find someone with 10+ years experience developing software, but in other countries you just have people who've stagnated and never moved up.
I dunno.
For eg: An executive an HCL , a leading Indian outsourcing firm called American developers "unemployable" :
>> He says students from countries like India, China, and Brazil are more willing to put the effort into "boring" details of tech process and methodology, such as ITIL, Six Sigma, etc.
http://www.dailytech.com/CEO+of+Microsofts+Indian+Partner+Co...
So basically , American devs want challenging work and technical growth , while Indian devs are happy to even have a job.
Dentistry and medicine are very lucrative careers in India.