In fall of 1945, the US Army began development programs for subsonic and supersonic cruise missiles, and for a ballistic missile (contracted to the Consolidated-Vultee company). These developed into the Navaho, Snark, and, eventually, Atlas missiles. At the end of 1946, President Truman ordered budget cuts (an event called "Black Christmas" for the number of programs cancelled) which led the Army to cancel the ballistic missile program (MX-774) and focus on supersonic cruise missiles. The justification was that the cruise missiles were believed to be an 8-10 year development program (more-or-less accurate, as Navaho first flew in 1956) while the ICBM (designed for a 5,000-mile range and a payload well in excess of one ton) was believed by experts of the time (like Vannevar Bush) to be over a decade off.
What if the experts believed otherwise and advised the cancellation of the cruise missiles instead?
The MX-774 contract led to a design very similar to, if bigger than, the Atlas that Convair eventually returned to. It had pressure-stabilized tanks, a central sustainer engine, and steered by thrust vectoring rather than vanes in the exhaust. As it was, the ballistic missile program reopened in 1951 due to the Korean War and yielded a missile in 1957. Suppose that the development program takes 8 years from 1947--so the MX-774 missile yields a ballistic missile equivalent to the OTL Atlas in 1955.
What happens next?
The US now has a rocket with more payload than the Soviet R-7, and has two years before the International Geophysical Year to shake it down. If they really want to (and disregard some of their OTL concerns about letting foreign scientists get too good a look at the missile), the Americans can send up a whole fleet of satellites before Sputnik is ready to go. Maybe even a manned capsule--the notional rocket certainly has the payload for it.
This rocket gives the Air Force effective supremacy over all missile-development efforts in the US--neither the Navy's Viking/Vanguard nor the Army's Jupiter are even close in range or payload, and the Atlas design is considerably more mass-efficient than those produced at Redstone Arsenal--so the Convair design philosophy will prevail over Von Braun's. The Germans might be totally marginalized next to the USAF.
An American ICBM up before the R-7 defuses the OTL "Missile Gap" scare--which robs JFK and LBJ of a lot of the momentum that drove them to success in 1958 and then 1960. So could this mean an early President Nixon?
With a high-payload satellite launcher on the horizon sooner, would there be more USAF interest in spy satellites (the first studies date back to 1947, but it was not until 1954 that they got more serious)? Could this bring about a program similar to Manned Orbiting Laboratory, but a few years sooner?
As a secondary POD, the US also studied nuclear-thermal-rocket ICBMs in 1947, concluding that, if a reactor of the right size could be supplied by the AEC, they'd be cheaper than chemically-propelled ones. The drive to develop them faded as payload sizes shrank, but suppose the US spends more on those (without cruise missiles to take funding) in the 1940s and 1950s, yielding at least a static-test NTR by the end of the Eisenhower Administration?