Differences in central bank interest rates.

The FED Interest rate is moving the stock market, but forex is more sensitive to the spreads.
In this simple aggregated chart, indexed to 100, several spreads between countries are shown.

For example, focus on the white continuous line, the US Dollar is more appetible for investor respect to Japanese Yen, because the UnitedStates has higher interest rate on its currency.

While, focusing on the red continuous line, the UnitedStates have the same interest rate of Canada. This means US Dollar and Canada Dollar have the same interest by investors in terms of interest on their currency. This means USD/CAD might be less dependant now from their central bank's monetary policies