The global nature of the economy means that stock markets often tend to trade in tandem. So with some major European stock markets down 2% or more on news of protests in Spain and Greece that call into question whether attempts to solve the financial crisis on the Continent will prove successful, it's reasonable to expect U.S. markets to follow suit. Yet even the combination of European trouble and weaker-than-expected new-home sales wasn't enough to send the markets down nearly as much as stocks in Europe, although a late-morning wave of selling sent the Dow Jones Industrials (DJINDICES:^DJI) down about 45 points just before 10:45 a.m. EDT.

Among Dow stocks, Hewlett-Packard (NYSE:HPQ) was on the downside again, falling about 2.5%. With an important analysts' meeting coming next week, HP CEO Meg Whitman needs to demonstrate her ability to develop and implement a strategy to address the declining PC market and move HP forward into more lucrative business lines. Investors have been extremely impatient with the slow progress in that direction so far, and the shares' performance reflects skepticism and doubt about the company's future.

Banking stocks in the Dow were also down, with Bank of America (NYSE:BAC) getting hit the hardest with a roughly 2% drop. The concern for B of A, Citigroup (NYSE:C), and other big banks is that if the European crisis flares up again, it's most likely to appear in Europe's banking sector -- especially in the vulnerable Spanish economy. Moreover, with Fed policy clamping down on long-term rates, B of A, Citi, and their peers can only do so much to boost interest income and profits. Citigroup also fell about 2% as it took measures to expand a team of workers focused on buying troubled assets from European banks.

Finally, Boeing (NYSE:BA) rose almost 1% as it deals with ongoing allegations from the European Union that the U.S. government is subsidizing the aircraft manufacturer in violation of World Trade Organization rules. Given that the U.S. has counter-alleged that Europe has subsidized Boeing rival Airbus, it seems likely that the dispute, after seven years and counting, will continue for a long time to come.

Fool contributor Dan Caplinger doesn't own shares of the companies mentioned in this article. You can follow him on Twitter @DanCaplinger. The Motley Fool owns shares of Citigroup and Bank of America. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Fool has a disclosure policy.