One of the most interesting cases, in my opinion.
We could also consider that, without the second world war particularly, the development of international football would have been accelerated, there would have been earlier World Cups with more genuinely global involvement, and players like Lenstra and Matthews would have played even more international games in these years. Some countries, such as Hungary, Sweden, Switzerland, carried on playing matches during the wars, so I haven't considered their players (although surely some players were affected anyhow).
Tom Finney (one of England's best ever players) couldn't begin his international career until 1946, when he was already aged 24. He won 76 caps.
Some other players affected, potentially:
Bernard Voorhoof (Belgium) 61 caps up to 1940, ending age 29.
"Jef" Mermans (Belgium) 56 caps from 1945, starting age 23
Armand Swartenbroeks (Belgium) 53 caps, 1913-28
Frantisek Planicka (Czechoslovakia) 73 caps up to 1938, ending age 34.
Antonin Puc (Czechoslovakia) 61 caps up to 1939, ending age 32.
Evald Tipner (Estonia), 67 caps up to 1939, ending age 33.
Heinrich Uukkivi (Estonia), 46 caps up to 1939, ending age 27.
Etienne Mattler (France) 46 caps up to 1940, ending age 34.
Edmond Delfour (France) 41 caps up to 1938, ending age 30.
Paul Janes (Germany), 71 caps up to 1942, ending age 30.
Ernst Lehner (Germany), 65 caps up to 1942, ending age 29.
Fritz Walter (Germany), 61 caps, 1940-1958
Giuseppe Meazza (Italy), 53 caps up to 1939, ending age 28
Renzo De Vecchi (Italy), 43 caps, 1910-25.
Eriks Petersons (Latvia), 63 caps up to 1939, ending age 29 or 30.
Janis Lidmanis (Latvia), 55 caps up to 1940, ending age 30.
Alberts Seibelis (Latvia), 54 caps up to 1939, ending age 32.
Romualdas Marcinkus (Lithuania), 41 caps up to 1938, ending age 30.
Puck van Heel (Netherlands), 64 caps up to 1938, ending age 34.
Harry Dénis (Netherlands), 56 caps from 1919, starting age 22.
Thorbjørn Svenssen (Norway), 104 caps from 1947, starting age 23.
Gunnar Thoresen (Norway), 64 caps from 1946, starting age 26.
Harry Boye Karlsen (Norway), 58 caps from 1946, starting age 26.
Reidar Kvammen (Norway), 51 caps, 1933-49
Lefter Küçükandonyadis (Turkey), 46 caps from 1948, starting age 22.
Stjepan Bobek (Yugoslavia), 63 caps from 1946, starting age 22.
Branko Stankovic (Yugoslavia), 61 caps from 1946, starting age 24.
Rajko Mitic (Yugoslavia), 59 caps from 1946, starting age 23.
Blagoje Marjanovic (Yugoslavia), 57 caps up to 1938, ending age 30.
Regarding the first world war, the great Welsh player Billy Meredith (48 caps) could have been the first player to win 50 caps*. Indeed, he should have done so anyhow: he was selected for more than 70 matches but on many occasions was not released by his clubs (Manchester City & Manchester United) for international duty.
* : if you wish you can think of Vivian Woodward as having more than 50 caps by combining his England and England Amateur caps. He could also have won many more caps but was injured during the war and did not play again at a high level.
On a similar subject, let us not forget that Russian / Soviet players were isolated from international competition until after WW2, so many great players were denied opportunities to win many caps.