You need a valid passport for travel outside of the United States. Visa requirements vary by destination, but are not generally required for European countries. Check here for the most up-to-date information.
Please be sure to check the expiration date on your passport as most countries require that your passport be valid for 6 months after completion of travel and many countries require at least 3 blank pages. You are responsible for obtaining and paying for all visa and entry documents and for meeting all health and other requirements of the countries you will visit.
If you need expedited processing for a passport application or passport renewal, click here.