Wrongfull Termination?

I Worked For A Company For 10 1/2 Years. I Climbed The Ranks Within The First 2 Years. I Was Given The Position Of Supervisor. After Another 5 Years, A New Branch Was Opening And I Was Asked To Be The Sup. For That Branch. I Accepted And I Helped Hire And Train 2 More Persons To Work With Me At That Branch. Two Years Later, One Of Those Persons Was Given A Review By Me And Was Upset With It. Since That Time, This Person Had Made It Unbearable To Work With, The Other Coworker Felt The Same Way. I Took It To The Manager And Human Resource Person. They Both Agreed That I Had Been Given The Training To Handle The Situation. The Next Review- Which Is Given To My Manager To Approve(which She Did) Was Given By Myself And The Manager. There Was Something She Did Not Like, So The Manager Changed It. I Discussed This With The Manager After The Review And She Stated That It Should Have Been Changed Before It Was Given. I Feel She Undermined Me In Front Of This Employee. And That Was Not The Only Time This Was Done, The Other Employee Cried For 2 Hours In The Office Before The Manager Changed Her Review And Pay! Before Sending The Reviews To The Hr Person For Filing, I Wrote An Accompanying Note Stating What Had Happened. Since This Time, I Was Told To Make The Branch A Better Place To Work In, I Feel I Had Been Accomplishing This, I Had Two Meeting With The Manager And Hr Which Are Never In My Office And Was Told It Was Not Getting Any Better. I Was Emailed At 10 Am To Come For A Meeting At Which Time I Was Terminated At 4 Pm, Given A Letter Which Stated That I Was Unwilling To Accept Responsibility For My Own Conduct And Have Been Argumentative And Resistant To Change. This Date Was 7/9 And The Letter Of Termination Is Dated 7/8 Stating That The 8th Was My Final Day Of Work. Do I Have A Wrongful Termination Case? And Should I Be Asking For A New Letter Of Termination Too? It Also Stated That At The End Of The Month I Would Lose My Health Insurance, It States In The Company Policy That The Insurance Is For 1 Month After Termination, Should I Be Fighting This Too?