have put many USA to Europe routes on sale.
For example, fly from New York to Amsterdam, Netherlands for only $399 roundtrip
There are far too many routes to find example dates for so try it out yourself.
Simply use Google Flights [google.com]
to find a working date, then click the GO TO DEAL button
below and proceed to book with Momondo [momondo.com]
New York/Philadelphia/Boston/Washington DC/Miami/Dallas/Phoenix/Los Angeles/San Francisco/Seattle/Chicago/Atlanta/Charlotte/Detroit/Minneapolis/Kansas City/Portland/Denver/Detroit/San Diego/Houston/Las Vegas/Orlando, USA
Availability from January to March 2018