The last Civil War before Shakespeare was the War of the Roses, which he was obviously aware of, since he wrote his plays: Richard II; Henry IV, Part 1; Henry IV, Part 2; Henry V; Henry VI, Part 1; Henry VI, Part 2; Henry VI, Part 3; and Richard III about the war, from incidence to bloody conclusion. But it had ended a century before his birth, and no public friends of the House of York survived to his day to talk about the downside. Also, as Civil Wars go, it had been rather mild, with most injuries to professional soldiers and hardly any damage done to non-military structures. If he had survived another 30 years or so he would have seen the real thing, in the English Civil War of Cromwell vs. Charles I.
Yes, too bad Shakespeare missed Oliver Cromwell and the English civil wars - In particular whose scenes where Cromwell had Charles I executed, and that famous scene where he marched his army into Parliament and dissolved it.
I’ve always admired Cromwell.
I have his picture on my living room wall.