Civ7 so far ends at 1960. Early Cold War. With earliest space race (sends a man to the Moon), or nuclear missile. JF Kennedy VS Kruschev. With Shermans and T34 still a mainstray AFVs of many countries and new generations like T55 and Pattons were only added recently, and so did assault rifles were only equipped special forces rather than regular rank and files. (much of post WW2 conflicts fought with residue WW2 weapons, even those introduced on the eve of 20th Century (Mauser Model 98 series, became postwar surplus sold or donated to armies or factions including Israel, Mosin-Nagant saw use by Communist factions and later states, particularly People's Republic of China, who used ones until 80s) or slightly at the early years (Lee Enfield rifles saw use by British Army in the post WW2 colonial conflicts, including Malayan Crisis ('Merdeka'), Borneo Border Conflicts (Modern Indonesia VS British Commonwealth team (Malaysia + Australia)) and successor nations (India, including their homegrown Ishapore derivatives. Indian footsoldiers used ones against Chinese who also used similiarly old bolt action service rifles and maybe some SKSs or SVT40s, in their border wars. Sikh rifle companies famously held ground against two brigades of Chinese forces with these.)
And all happened when Soviets already mass produced Mikhail Kalashinikov designed assault rifles.