Complex sentence: It followed a growing national sense that U.S. scientists were falling behind scientists in the Soviet Union, catalyzed, arguably, by early Soviet success in the Space Race, notably the launch of the first-ever satellite, Sputnik, the previous year.
Split into simpler sentences: It followed a growing national sense that U.S. scientists were falling behind scientists in the Soviet Union. The early Soviet success in the Space Race catalyzed a national sense of unease with Soviet technological advances, especially after the Soviet Union launched the first-ever satellite, Sputnik, the previous year.