Same applies to all eastern European countries, Japan and China. People start prepping when they're still in middle school. Most of the winning team members are former IOI gold medalists.
BS, not a lot of people give any F's in Poland, yet 3 regional universities almost always place at the top. Lets face it, its the level of education (socialized = free in regions you listed) versus western broken for profit model.
Most western universities and colleges are not for profit. They're not free, but they're heavily subsidized, directly and indirectly. Princeton for example receives $105,000 per student per year in benefits due to the fact that none of their land is taxed, nor do they pay any capital gains taxes on their investments.