Why monitoring the political and economic scenarios of countries are important to global Forex trading?

As it has been observed statistically, the value of currency of a country changes a lot due to the economic and political climate of the country. For example, the Federal Rate cuts on Interest rates aimed at controlling the sub-prime crisis in USA increased the value of the US Dollar. Don’t get carried away of you get a cue from one such indicator. Please make a list of all such factors that would impact a currency in the Forex Trading Market.
A long pending factor to a currency movement is the price of crude oil per barrel. As the price of crude oil inches towards $100 per barrel, the US Dollar is inching towards new lows by the day. In such a scenario, you would think that the US Dollar could be undermined severely