America's best years of peace, prosperity and strength came under Liberal governance? Really? Care to examine the examples you posted?
FDR: Great Depression and WWII. Pretty good at the Strength thing, but a Fail on peace and Prosperity
Truman: WWII, Onset of the Cold War, the post-war recession and Korean War. Started out okay on strength, but whittled it away after VJ Day. Had Two wars and a recession under his watch, so not so good on the peace and prosperity part.
Kennedy: Bay of Pigs, Cuban Missile Crisis, began direct involvement in the Vietnam War, accelerated the nuclear arms race; butr did manage to enjoy prosperity by lowering taxes on the rich.
Johnson: Greatly expanded the Vietnam War, and... what?