Does one bad play lose the game?

the OP is correct that any number of plays could change the outcome. However i do think coming though in a crucial situation can win the game for your team, just as falling short in a crucial situation can lose the game. Typically these situations take place in the 4th quarter where close matches are decided. for example, one could say Karney lost that game in 2003 against the Jags (river city relay).