I would like to travel mostly in France and be able to visit a number of other western European countries for 6 month period. I understand that I need a French visa, do I need one for the other countries? Do I need to get the French visa at a French embassy in the U.S.? If I decide to stay longer than 6 months in France, can I apply for a longer visa while in France? I am retired and will not be looking for work.
The information you seek can be found on the website for the French consulate for your area. (There are several French consulates in the US and each one covers a certain area of the US) If you are retired and won't need to work, have sufficient income and health insurance to cover you while you are in France, you should be able to apply for a "visiteur" visa with a duration of 1 year. That visa would be renewable from within France if you desire. If you are traveling to the other countries for short periods of time, but maintaining residence in France, then you would not need a visa for the other countries.
Dina is amazing.