I have a crossover fanfiction of Mass Effect and S.M. Stirling's Draka series over at FanFiction.com. [link]

For those unfamiliar, the Draka series takes place in an alternate universe where the American Revolution goes slightly differently and the British take over South Africa from the Dutch much earlier. The Loyalists from the American colonies, after the rebels successfully gain their independence, are resettled at the Cape Colony to secure it for Britain and it's renamed the Crown Colony of Drakia, named for Sir Francis Drake. Drakia, whose name is eventually shortened to Draka, expands from their initial settlement throughout Africa through the 19th Century, enslaving its various peoples and using the gold and diamonds of South Africa to fuel the continent's industrialization. With another industrialized power - eventually called the Domination of the Draka - the technology of this universe advances much faster than ours. The Domination becomes a sort of 'anti-America', the fusion of all the ideas and philosophies that were rejected by Western civilization.

The Draka series starts during this universe's version of World War 2 in the book 'Marching Through Georgia', and continues with 'Under the Yoke' and 'The Stone Dogs'. These three novels are collected in a compendium called 'The Domination'. There is also a later novel called 'Drakon' which takes place in its far future.

In my fanfiction, the Prothean bunker on Mars is discovered much earlier than the original Mass Effect, and both series are irrevocably changed.