在 ACM竞赛中，为什么美国的公认的计算机名校，如 MIT，斯坦福、加州伯克利、卡内基梅隆，表现不如中国和俄罗斯的高校？

知乎上看到的比较好的解释：

是这样，我在美国念书，去年的时候我参加regional比赛时我们赛区有些非常出名的计算机学校，但是我们很轻松的就把他们秒杀了，还差一点进final。其实这个问题说起来很好解释，我上大学之后明显编码水平下降了， 因为在北美念书你会发现主要做的都是一些开创性的工作，整体教育体系是不赞成学生做大量重复性工作的。在美国主要是培养的你的一种学习和创新的能力，也就是为什么美国培养了大量的顶级计算机科学家和工程师，但是国内好像除了一些竞赛获奖之外听不到太多的好消息了。
另外澄清一个问题，美国人的数学并没有那么差，中国人的数学并没有那么好。论顶尖学生还是美国本土培养出来的多，无论净量还是比例都是。中国将近14亿人培养出来那几个稍微强一点的真不能说是什么功绩。

顺便说说阿三，要是看阿三的竞赛成绩其实非常糟糕，但是他们毕竟创建了tata还有Infosys之类非常优秀的软件公司，而且Google I/O的时候真的觉得阿三讲的比老美都多……看过3 idiots这个片子后就明显感觉到，印度这个国家在改变，尤其是教育理念。反观我天朝大国的教育，其实这些竞赛奖还蛮讽刺的

在一个外国网站上看到的比较好的解释：

As Robert mentioned, I think the main thing is that the level ofcompetition has increased to an amount of commitment beyond whatmost people are willing to put in. I 
was a coach at the ACM ICPC in 2005and heard a similar story about the Shanghai Jiao Tong University teampracticing all day for the entire previous summer. When I was on theCaltech team, the team members weren't decided until a few monthsbefore the contest, and we only practiced a few hours a month, mainlybecause everyone on the team had other competing demands on theirtime.

In the US, the best students have opportunities to do research withprofessors that will lead to them basically being guaranteed admissioninto a top graduate school, 
they have easy access to internships at thetop companies, and they don't have as much to gain by winning. In othercountries, especially with worse economies, there 
aren't as many goodalternative ways to spend time, and doing well can significantly increaseeveryone's opportunities. The cultures in those particular countries  alsoreinforce math and science and increase the pool of potentialcontestants.

I think this is mainly true of ICPC - if you look at the IOI (a high school contest) there are a much wider variety of countries represented among the top finishers, though Russia, China, and Poland are still strong there too.