It is useless because the definition of a college degree is different from country to country.How can you compare it for example with Russia when basically they do not have a college degree ? The basic unit of comparison is wrong, because in North America it's Bachelors and in Eastern Europe it's Masters. Does a graph mixing feet and meters is useful ( although both measure a distance) ?

Flawed, sure, but not useless. Lining up the countries side-by-side isn't very informative, but looking at the generation gaps within a single country can be.

For perspective, the title of the study this chart came from is "The Accelerating Decline in America's High-Skilled Workforce: Implications for Immigration Policy". The authors are looking at which countries are creating lots of new high-skilled workers, and which are heading into a deficit of high-skilled workers (Germany and U.S.). In general, education systems from different countries don't map very well onto each other, but on the issue of high-skilled immigration into the U.S., the unit of comparison is "education level that U.S. companies/politicians would consider high-skilled". So, of course it's flawed and U.S.-centric -- it's a chart about U.S. immigration policy.