Yes, but what about when the shareholders are also mostly Americans? Big corporations tend to operate in their stock's best interest, and this can still cause serious problems for their shareholders.
Erm, what? This seems contradictory on its face. The shareholder's only interest in a company is its stock performance, be it stock price or dividend payments. What sort of tendencies are you thinking of, here?
I think this is where you and he differ.
For instance, I'm a Microsoft shareholder. (2 shares, but still...) Many Microsoft decisions since the mid-90s (when I first started holding MSFT) have made life overall worse for me, even if they may have increased the value of the stock I held.
That has nothing to do with your being a shareholder.
Consider the case of a shareholder invested in a company behaving in anti-competitive behavior that negatively effects the market as a whole. Now suppose the same shareholder owns many stocks across the market. This is clearly a loss for the shareholder, and a win for the company only. That's what I was trying to express.