[Update: I tried to purchase a $350 ticket for Edinburgh to San Francisco about 10 hours after publishing this post to find the fares went up to $700s. I have seen these deals before and they are likely to return.]
One of the sweet spots for low fares from Europe to the USA are cities in the UK with fares as low as $304 round trip to Las Vegas, Los Angeles and San Francisco.
Belfast BHD, Manchester MAN, Edinburgh EDI, Glasgow GLA and Inverness INV are airports with low fares and low taxes for flights to the USA. This post focuses on LAS, LAX and SFO. There are deals to many other cities like Miami and New York.
Low fares are available every month April 2017 to February 2018, except for July.
American Airlines Inverness INV – London LHR – Chicago ORD – San Francisco SFO – New York JFK – London LHR – Inverness INV
British Airways Edinburgh EDI – London LHR – Los Angeles LAX – London LHR – Inverness INV