One more solution from Europe to USA today based on a Star Alliance promo sale (see also our solution from Scandinavia / France to Denver from €279) this time discounted deal from Italy or the UK to California. Return flights from main airports in Italy (Bologna, Venice, Milan, Turin, Rome) to Los Angeles are available already for €327 or from the UK (Edinburgh, Glasgow, Manchester) to San Francisco already for £290. Again you can fly on various airlines such as Lufthansa, Swiss, United or Air Canada so choose the routing and carrier you prefer..
Travel restrictions of this Lufthansa (and their partners)promotion: Fly from 10th of April to 24th of June or 21st of August to 19th of December 2018. Max stay 1 month. Promo sale is running till 12th of March or until the cheapest seats last. Need an accommodation in San Francisco or Los Angeles you can use service of Hotels.com or Booking.com.
Scandinavia – USA from €232 (Lufthansa flights but no checked bag in base fare)
London – Oakland from £354 (British Airways non-stop flights)
Booking sample of promotion offering Star Alliance cheap flights to California from Italy €327 or the UK £290! Your outbound flight from Edinburgh from San Francisco would be on Friday, 31st of August 2018 and returning back from USA to the United Kingdom on 16th of September.