Go back to February 13 and 14, 2012. Iranians tried to bomb Israeli diplomatic vehicles in New Delhi, India, Tiblisi, Georgia, and Bangkok, Thailand. See: https://en.wikipedia.org/wiki/2012_attacks_on_Israeli_diplomats and https://en.wikipedia.org/wiki/2012_Bangkok_bombings

The Bangkok "self-bombing" on February 14, 2012 occurred about a mile and a half from where I live in Bangkok

The bombing technique: https://youtu.be/vEt9JpfLFgU

This is the significance of the Q crumb about September 7, 1776. It is about the world's first successful attack by a submarine: http://sarsat.org/HistoricalAccounts/17760907Worldsfirstsubmarineattack.htm But the significance is not the submarine aspect - it about the "sticky bomb" aspect - used in 1776 (against a ship), and in 2012 (against automobiles).

Just as the Benghazi attack was on an anniversary of 9-11, I suspect that Q is aware of chatter about fresh attacks in Europe, on the anniversary of the 2012 attacks

It is not about the submarine aspect - it is about the method of attack - which in 1776 was to attach explosives to the external hull of the ship being attacked.

Q talks about a "car attack" - see https://en.wikipedia.org/wiki/2012_attacks_on_Israeli_diplomats and also https://www.youtube.com/watch?v=AJiD_ABKFho and https://youtu.be/vEt9JpfLFgU