International and Inter-League Gridiron Football has been played since at least the 1920s.
The first match that could be described as an International Gridiron or American Football match is the one between two AFL teams in Canada in 1926. Following this the NFL and AFL played a series of matches between the Leagues in the 1920s, 1930s, and 1940s.
In 1941 the first Canadian Football League v American Football League matches were held, and in 1950 the first match between a National Football League team and a Canadian Football League team.
Beginning in the 1970s, there were attempts at promoting American Football in Europe, through the Intercontinental Football League, and from there the World. In 1976 the St. Louis Cardinals and San Diego Chargers played in Tokyo. In 1984 two United States Football League teams played in London, and in 1986 the first NFL American Bowl preseason game was held in London.
In 1999 the first World Cup was held, involving USA, Canada, as well as four other Nations which have to qualify through a series of matches.
In 2007 the NFL decided to promote the NFL in London, Mexico City and Toronto with the International Series of Regular Season games, which have run until the present
Major Inter-League American Football
American Football League (1926); NFL v AFLs 1927-1936; NFL v Army 1942
American Football League International
National Football League v American Football Leagues 1927-1942
Whilst not strictly speaking International matches, the National Football League has also played matches against American Football League teams in the 1920s, 1930s, & 1940s.
Picture Credit: [International 1] Ninety-Nine Yards, Chris Lawton (2020) An International Fixture: When the CFL played teams from other leagues [Internet] Available from: https://i0.wp.com/ninetynineyards.com/wp-content/upl
Canadian Football League International
AFL in Canada 1926; CFL v AFL 1941-1948; NFL v CFL 1950-1961; NFL Preseason in Canada 1960-1969
Canadian Football League Internationals:
National Football League Preseason American Bowls
NFL International; USFL International; The Spring League v Japan;
National Football League International (Preseason Games):
AAA Leagues Internationals
National Football League International Series
NFL in Mexico 2005-Present; NFL in London 2007-Present; NFL in Canada 2008-2013
National Football League International Series (Major League)
Minor American Football Leagues International
Intercontinental Football league; Arena Football League; The Spring League; USFL; Legends Football League
AAA American Football Leagues International
AA Minor American Football Leagues International
Intercontinental Football League European Championship (Seasons):
Picture Credit:  Global Football | Michael Preston (2015) When Global Football, the Irish & Midshipmen Rocked Dublin [Internet] Available from: http://www.globalfootball.com/wp-content/uploads/2015/10/681161-copy.jpg [Accessed 17 January 2020]
USA and Canadian Colleges Internationals
US College Division I Teams Abroad; US College Division III Teams Abroad; Global Football;
NCAA Division I Football Games Abroad:
NCAA Division 1A Freshmen Tours to Europe
NCAA D 1A Freshmen Tour of Britain (Results): 1998
NCAA Division 1AA Football Games Abroad
NCAA D 1AA Tours to Europe (Box-Scores): Villanova Wildcats 28 Rhode Island Rams 25 Milano Kickoff Classic Italy 1989
US College Division III Football Games v World Opposition
US College Division III Football Games Abroad
Global Football NCAA v CONADEIP (Mexico) Tours to Africa (Seasons): 2011
Global Football NCAA D III Tours to Europe (Seasons): 2019
Canadian High School Tours of Europe
Team Canada HS Tour of Britain (Season Results): 1998