Alterac was destroyed by Stromgrade after they betrayed the alliance in the 2nd war. The remaining people of Alterac are know as the syndicate.
Stromgrade fell into ruin just shortly after Danath was lost in Outland. And was fully destroyed when thrall escaped for durnhold keep. The kingdom was rebuild by Danath and his forces in BFA.
Lordaeron was destroyed and most of its people did become forsaken, but not all of them. Also the forsaken are not all human.
Stormwind was destroyed in the first war. The Stormwind you see know is the one that was rebuild after winning the 2nd war.