As usual, pre-TV teams aside — otherwise Argentina, Italy, Uruguay & Austria would've certainly been picked from that era.
West Germany: 1972 Euros, by far. Unstoppable, entertaining, ruthless.
England: 1966 World Cup. Kind of an obvious one considering that this is the only big international trophy that they've ever won.
Denmark: 1986 World Cup. The swan song of Danish Dynamite, brutally interrupted by the insatious vulture.
France: 1984 Euros. It's a coin-toss between this and the 2000' team, but I'd go with Platini's crew as it makes sense to pick a team with the best French player ever in it.
Italy: 1982 World Cup. It's not obvious at all as you have the 1990' and 1970' teams that weren't far off as well as being very similar — world-class defense and some monster up front, but I'd go with the winners.
Spain: 2010 World Cup. Inevitable.
Netherlands: 1974 World Cup. It doesn't require an explanation.
USSR*: 1988 Euros. Even though I rate the 1960's generation higher, there were always some issues — injuries, scandals, politics etc. that stopped that team in reaching their true potential. The 1960 winners were great, but Lobanovsky's machine from 1988 was something else. The way that they've eliminated star-studded Italy in the semi-final
Belgium: 2018 World Cup. The best campaign of their most talented generation.
Ireland: 1988 Euros. They've reached later stages in the 1900 World Cup, but I feel like their performance 2 years prior was better. They were drawn into the group of death, beat England and played very well against both of the eventual finalists.
Wales: 2016 Euros. The only time when they were relevant on the international stage. Incredible effort from that side.
Portugal: 2000 Euros. It's debatable, but this is my favourite side of theirs. 2004 Euros & 1966 World Cup are obviously in contention.
Hungary: 1954 World Cup. Best national side in history?
Poland: 1974 World Cup. They genuinely looked very close to both Netherlands and West Germany in quality when those footballing giants were both having their golden generation moment.
To be continued.
