You might three passport date issues:
1 -- You can get back into the U. S. if you have a passport that is still current to the expiration date. (I fudged this once by returning late through stupidity and got in with a short quizz and a wallet-dump which took all of two minutes.)
2 -- Different places require varying amounts of time left on the passport for intitial entry into that country. If you're going to be outside the Schengen Zone on the trip, check what's required for those places.
3 -- If you do go outside the Zone and come back in, you will still need three months left on the passport from that date. The exception here is if you're only transiting the Zone (e.g.; changing planes in Paris while flying from Moscow to New York), the three-month business does not apply.