>Why is this external sense of achievement important to humans seemingly?”
TV doesn’t tell you, but most people don’t participate in regular organized sport, and many, possibly even most are not that interested in organized sport.
Way back in the EoEA being good at something, some specialty, got you some social status and a root, DNA recombination possibilities, helped with raising offspring to breeding age too, and as it went rather than dragging another into the cave or whatever they turned up obliging-like. Not unlike those girls that turn up to parties involving their favourite sports stars.
As for competitiveness, humans have enough of that without ideological amplification.
Much as the “team” and ‘us’, and ‘we’ etc are apparently important, much of the work of social life involves limiting the power of groups over individuals, though the ideological apparatus is not terribly forthright regarding that, more it’s like a demanding toddler with ADD, with the added dimension of passing itself off as something akin to a force of nature.
Probably look to phylogeny and selection pressures of groups past, way back, look to what shaped the social instincts and social receptiveness. You’ll maybe find much of the modern apparent convergence of neural activity is largely the product of modern culture, since taken to an industrial scale.