Besides the major powers like the US and Russia who would be the obvious answers, which countries are known for being very good at both winter and summer sports?
With Norway and Canada's breakthrough performance at this year's World Cup (quarters for Norway and R16 for Canada; two countries historically more known for winter sports), I feel like both of them have to be among the front-runners for this question.
In summer sports, Norway has the world's best striker (Haaland), a 9x NY Marathon winner (Grete Waitz), the best middle distance runner in the world (Ingebrigtsen), one of the best hurdlers in the world (Warholm), a 3x grand slam finalist (Ruud), top 10 golfer in the world (Hovland), and the greatest chess player of all time if that counts too (Carlsen).
In winter sports, Norway needs no introduction as they regularly top the medal count at the Winter Olympics with some of the greatest winter athletes in the world in alpine skiing, biathlon, speed skating, and cross-country.
For Canadian summer sports, they have one of the world's best LBs (Davies), the b2b reigning NBA MVP (SGA), one of the greatest decathletes of all time (Warner), the world's best female swimmer (McIntosh), two top 10 players in men's/women's tennis (FAA and Mboko), one of the GOATs of women's football (Sinclair), two of the world's fastest men in their eras (Bailey and De Grasse), a former F1 world champion (Villeneuve), and a former Masters Champion (Weir). They also produced one of the most badass dudes of all time, Terry Fox.
In winter sports, the Canucks need no intro either as they're a modern powerhouse in the Winter games, especially in disciplines like ice hockey, curling, freestyle skiing, figure skating, and speed skating.
Historically though, I think neither of them can top Sweden as Sweden in the late 20th century was truly a global sporting powerhouse in several winter and summer sports.