Question

while soviets rejoiced in the success of the sputnik program, americans?

Answer 1

...freaked out about it. The Soviets essentially beat the United States into space demonstrating that they were ahead in the rocket race and it was a severe blow to national prestige prompting an accelerated program to catch up with them.

But there was also a military concern, too. Because the Soviets were able to launch a satellite into space, it essentially told the US that they had the technology needed to build advanced long range missiles. It's the same kind of concern that have focused a lot on North Korea's satellite launches in the past and why many believe that it was only a smokescreen to test new missile designs.