The current growth policy of the US government is built on increasing debt, and a slow, steady currency devaluation. If the value of the currency appreciates, that debt gets more expensive relative to other currencies and assets. So, a strong dollar creates problems for debt servicing. Secondly, as the dollar is still the reserve currency for commodity assets, when the dollar strengthens, commodities fall in nominal terms. With a globalized economy, most american multinational corporations have their revenue base in other currencies, in which they use to repay their borrowed dollars.