Do you really cost your team the game, though? Is the blame squarely on your shoulders?
Assuming all things are even:
If your bot lane teammates get caught in a gank by a strong jungler like Vi or Lee Sin, and you're not there to counter the gank, that is a mistake on your part. If your teammates get killed, that is a mistake shared both by you for not anticipating the gank and being prepared for it, and by your teammates for putting themselves into a dangerous position.
You can mitigate this mistake by making a play mid or top lane though. Or by counter-jungling Lee Sin while he's busy bot lane (though I confess, counter jungling with Amumu is easier said than done).
Bronze and Silver players, myself included, constantly make mistakes. I see it in my own play, too. I should've done that, or I could've done this. Enemy was in range for a free AA and I missed it. I forgot to put a ward there and now I'm almost dead because I got caught. They make mistakes constantly every minute. Most times it's positional mistakes, or missed retaliatory trades, but they are there, and they are frequent. The magnitude of mistakes may vary and certainly will intensify the later into the game you go, but no one is ever completely blameless.