With the Black Widow still under the control of Soviet sleeper agent Leo Novokov, the Winter Soldier‘s world implodes as he sees the damage his lover does to S.H.I.E.L.D., including nearly killing Nick Fury.
To help track down the Black Widow, who still believes she’s a Soviet spy who has been working undercover for years, Captain America shows up with a pair of Avengers in Wolverine and Hawkeye (meaning the “secret” of Bucky’s survival lasted less than a year).
It’s unlikely the Black Widow will stay lost for long and, yes, there will be some guilt over her actions and the death of Jasper but no real lingering effects to the overall Marvel Universe. The only way this story has any lasting meaning is if the Black Widow had killed Nick Fury (which didn’t happen, and I don’t see any reason a character with the savvy of Fury would have put himself in position for her to try) or if Bucky is forced to kill Natasha (which won’t happen either). Still, it’s well told and worth a look.