Without Lyndon Johnson becoming President the United States avoids both the Great Society, and the Vietnam War.
Without the Great Society the economy isn't overburdened with taxes and regulations, and American Society isn't torn apart by Government mandated in Social Engineering and Experimentation.
Without the Vietnam War, the radical left focuses on Anti-Nuclear and Pro-Palestine causes.
Without Vietnam the U.S. Army undergoes a modernization program and leads to the deployment of anti-tank guided missiles on a larger scale a decade earlier. More forces are available for deployment in Europe, Japan, and South Korea.
Further, The United States would never have lost a war, and maintained it's huge advantages in nuclear weapons. The effort to allow the Soviet Union to "Catch Up" in hopes they would stop, and the concept of "Mutual Assured Destruction" created by Robert McNamara, would never have taken place.
From WW2 to Vietnam the ability to bomb a railroad bridge was the same. Without Vietnam it would have taken longer not less time. Without the Great Society we would have thrown the poor under the bus earlier than the GOP did in OTL.