Exchange rates are the net result of trade in goods and services (and capital), it's the bottom line fudge factor that makes trade work. If a country imports too much, its currency drops making foreign goods more expensive slowing imports. If it exports too much, its currency rises making its goods more expensive and slowing exports.
If the US imports a lot, it sends dollars overseas. If the foreigners want to invest in the US economy, those dollars come back in exchange for assets and the value of a dollar is not affected. If the foreigners don't want dollar denominated assets, they just buy their preferred currency instead, sending the dollar down. (In the case of investment, the US for most of its history ran a huge trade deficit. It was not a problem because economic growth meant foreigners wanted to invest here. Much of the trade deficit was caused by the purchase of capital equipment, used in driving the economy)
People who are thinking about exchanging currencies are not doing it on whim, they are doing it for underlying reasons that have to do with economic activity, productivity, long term investment opportunities, etc. These things carry currency denominated prices, but those currency fluctuations do not affect the rates of return of the investments, rather those currency fluctuations are how the books are balanced and change the rates of ebb and flow.