In an alternate reality, the Romulan war was canonized as this: http://www.aintitcool.com/node/34635
Cloak-equipped Romulan drone ships fighting United Earth Stellar Navy fighters in Earth orbit for a week in October 2159, as Tiberius Chase and Skon fly the stolen warp 7 prototype USS Spartan toward Romulus, with an old nuclear weapon (stolen from Terra Prime) on board.
As for Star Trek: Enterprise
's continuity, they simply ignored Spock's little mission broadcast from "Balance of Terror". No use trying to work around it. It's simply been dumped with James R. Kirk, "Time Warp" drive, lasers, "Bill" Riker and lithium crystals in the bits of Trek that don't count anymore.