I’ve completed this seasonal event a few times now, coming 1st in every race, my team winning every race, still no reward given. I can only think that it’s not functioning as intended.
Video of the 4/4 wins and finishing 1st only for it to say the challenge is incomplete: Star-Spangled Seasonal Event Bugged! - YouTube
My experience was on PC, though it seems as if it’s not platform dependent.
I think the event is bugged on Xbox as well, I’ve done it 5 times now and still no green man suit. I would post more about wins and stuff but hopefully turn 10 gets the drift on what’s going on and fix it, they are quick on fixing glitches but not fixing thing like this is kinda annoying, even on horizon 3 I have achievements that I know are done but after how many years since that game came out and it still isn’t fixed (facepalm)