How are congress and the president involved in the armed forces?

The president is allowed to state whether he wants a war to happen or not, congress must pass or deny his decisions on starting war/buying materials.

The president is involved by being in the excutive branch he gives off diffrent info and orders for diff things

Currently, as of february 2016, an american traveling in france would be by the exchange rate. the weakness of the euro and the strength of the us dollar means that items in france cost less to an american than they otherwise would. of course, if this trend reverses and the us dollar weakens and the euro strengthens, such as was happening in early 2008, an american traveling in france would have an adverse experience because items would cost relatively more.