What is a libreria de viejo and where are they found

It means old library or a place that sells old books.  They can be found in Paris as well as Madrid.  They usually sell very old and very literary works.  There is a big demand for such books for their high value and rare works.

Yes.

Explanation:

Yes, there has been no declared war since World War II, yet the US has been almost constantly engaged in military action because United States want to control the whole world and main his supremacy. So for that reason, United States is constantly engaged in military actions which cost them a lot on the economy. Congress “authorizing the President to use force” means to use the force for defending its own interests while declaring war is a full fledged war against country or community. President bears more responsibility in each case because he is the head of the country. Declaring war needs more resources and money for the war and soldiers which greatly effect the economy of the country while using force for a particular mission does not need more resources and money so using force is better than declaring war.