Actually, most European countries invest at a considerably higher rate than the United States. By comparison, the United States devoted just 17.1 percent of its GDP to investment. Both articles imply that the relative rates of growth of economies determine the exchange value of their currency. Therefore, since the United States is growing faster than Europe, it is reasonable to expect the dollar to rise against the euro. There is no economic theory that supports this view.
Investors care about maximizing the return on their assets.
A high rate of growth in a country does not imply a high return on financial assets, particularly if a nation's currency is over-valued. For example, the U.S. dollar fell sharply against European currencies in the late '70s, even though it enjoyed a more rapid rate of growth than most European economies. If the dollar does not fall significantly at some point in the near future, then the United States will have accumulated a level of foreign debt that is clearly unsustainable. Given this debt, it is reasonable to believe that at some point investors will anticipate that the U.S. will not be able to continue to borrow at its current rate, and that the dollar will therefore fall in value. When investors anticipate this fall in value, they will sell off dollars, which will actually bring about the fall in value.