realistically, cant blame him.
they were definitely a favorite but nothing you can do
a solution is just gamble on ez picks ig, wait for emea/americas/apac stage 1 games to start and bet on like nrg to win vs furia or sum shit.
good luck
you probably new to esport. american really bad at esport almost every game. they usually got some hype by media or fans. next time try to bet at asian team, u would get some money back