Can I ask, are you a long term trader or a short term trader.
This may seem like a silly question at first, however if you are a 'day trader', or rather a trader who holds positions for less than perhaps 48 hours then the above question wont really effect you, or rather your trading approach to be more specific.
Even in the most bullish markets there are pullbacks, and in the most bearish markets there are pullbacks. In hindsight, and depending on your own trading style, either the main trend or the pull backs could be traded. You mentioned that you are interested in USD; [as proof of my above comment you can look at the six months from the starting date of 01/08/2008 - the latest financial crash. Considered as the most severe bearish market conditions in the last 10 years. However, as obvious as the bearish conditions are, there were still opportunities to buy USD pairs on pullbacks when trading short term]
The point that I'm trying to get towards [all be it a very simplified description] is that long term economic views, such as a war or political disagreement still allow you to either trade with the trend or against it when trading on shorter time frames.
Now, should you be the type of trader who will be holding open positions for a number of days or weeks; your question becomes very very relevant towards your own success as you are in essence trading the economics which drive the longer term trend of the markets.
This is of course just a basic insight, and some traders will argue that trading with the longer term trend is the only way to go, however, I'm inclined to disagree depending on how risk adverse you are as an individual.