Great counterfactual.
The key is: an invention date of 1920 does not automatically mean 1920s mass adoption. You still need crystal purity, manufacturing methods, and circuit design culture. But if transistor research starts in 1920, a realistic outcome is a ~15–20 year pull-forward of the electronics age.

Working assumption

• 1920: transistor effect discovered + demonstrated.
• Late 1920s–1930s: usable devices for specialized applications (communications, military, instrumentation).
• 1940s: mature transistor production.
• IC-like integration appears in the 1940s/early 1950s (instead of late 1950s).
• By 1980, tech level might resemble something closer to our mid/late-1990s in computing density, but unevenly distributed.

---

1) 1920s–1930s: early semiconductor era begins

First-order effects

• Faster progress in telephony repeaters, radio receivers, hearing aids, and military comms.
• Less dependence on fragile vacuum tubes for some applications.
• Earlier investment in solid-state physics (US, Germany, UK, Netherlands).

Second-order effects

• Universities create semiconductor programs in the 1930s, not 1950s.
• Firms like Bell/GE/Siemens/Philips build semiconductor divisions earlier.
• Radio and communications gear become more portable sooner.

Third-order effects

• Labor-market shift: earlier demand for electronics technicians; less for electromechanical relay industries.
• During the Depression, early automation/electronics can worsen unemployment pressure in some sectors, feeding political extremism.

---

2) WWII (1939–45): more electronic, faster, more decentralized war

Likely direct military changes

• Smaller, more reliable field radios improve tactical coordination.
• Radar sets become lighter and more numerous (especially airborne/naval).
• Fire-control and fuzing electronics improve anti-air and naval combat.
• Early digital/logic machines for cryptanalysis and ballistics appear in larger numbers.

Who gains most in WWII?

• Initially: countries with strong prewar electronics ecosystems—Germany, UK, US.
• By mid-war: US gains most due industrial scale + quality control + mass production.
• UK benefits strongly in radar/crypto; Germany may gain early tactical advantages but struggles to outproduce Allies.

Net WWII outcome

• War likely still ends in Allied victory (industrial and resource asymmetry remains decisive).
• Could end slightly sooner in Europe if Allied radar/computing/logistics advantages scale faster.
• But an alternative branch: better German guidance/electronics could prolong specific campaigns (air defense, missiles), increasing short-term casualties.

---

3) Nuclear and early Cold War (1945–1960): command, missiles, and computation advance earlier

First-order effects

• Faster transition to transistorized military electronics.
• Earlier miniaturized guidance for missiles and aircraft.
• Earlier computerized air-defense and signals intelligence systems.

Second-order effects

• ICBMs and SLBMs become accurate earlier; deterrence becomes robust sooner.
• Nuclear command-and-control gets computerized earlier, improving response speed.
• Civilian computing enters government and large firms by 1950s at larger scale.

Third-order effects (important)

• Hair-trigger risk increases earlier: faster warning/decision systems can amplify false-alarm danger.
• Intelligence/surveillance states (USSR, East Germany, etc.) get better data processing earlier.
• Export controls on semiconductors become central Cold War policy earlier than in our timeline.

---

4) Space race: starts earlier, becomes more automated

Likely timeline shifts

• Satellite electronics miniaturize earlier, so first practical satellites could be moved up by several years.
• Guidance computers for launch vehicles mature earlier.
• Crewed spaceflight may move up modestly (rocket propulsion and life support still bottlenecks).

By 1980

• More capable satellites earlier: weather, reconnaissance, early navigation constellations.
• Space competition may be less symbolic and more systems-driven (ISR, targeting, telecom dominance).

---

5) Consumer electronics and computing by 1980

Likely pull-forward

• Portable radios and consumer transistor devices become common much earlier.
• TV, hi-fi, and solid-state appliances diffuse sooner.
• Integrated circuits and microprocessors appear earlier -> personal computing emerges earlier.
• Digital switching and data networks start earlier; proto-internet expands sooner.

By 1980 in this timeline

You might see:

• PC penetration resembling late-1980s/early-1990s real-world levels.
• More advanced video games/home computing.
• Earlier software industry concentration (US, maybe Japan, UK clusters).

---

6) Economic structure: winners and losers

Biggest beneficiaries

1. United States (scale, capital markets, R&D ecosystem, wartime mobilization).
2. Japan (postwar consumer electronics export machine starts earlier).
3. West Germany (strong industrial-electrical base postwar rebound).
4. UK/Netherlands (early scientific leadership, though scale limits long-term dominance).

Relative losers

• Economies dependent on late industrialization without electronics ecosystems.
• USSR likely keeps military parity in niches but falls behind in mass semiconductor quality/yields by 1970s.

Structural macro effects

• Earlier productivity gains from automation.
• Earlier shift toward high-skill services and electronics manufacturing.
• Earlier globalization of electronics supply chains (and earlier strategic chokepoints).

---

7) Unexpected consequences

• Propaganda and mass media effects amplify earlier (portable radios + TV diffusion).
• Cybernetic governance/technocracy becomes fashionable earlier in both capitalist and socialist blocs.
• Financial digitization (clearing, trading, risk models) arrives earlier, potentially making 1970s financial volatility sharper.
• E-waste/toxic manufacturing issues appear earlier (solvents, heavy metals, disposal).

---

Bottom line

A 1920 transistor most likely gives the world a 15–20 year acceleration in electronics, not a total rewrite of history.

• WWII: tactically more electronic, strategically still likely Allied win.
• Cold War: earlier and more intense techno-competition, with both stability (better deterrence) and instability (faster crisis escalation).
• By 1980: a much more computerized, networked, and surveillance-capable world—economically favoring countries that combine materials science + manufacturing scale + system integration.