Answer
$0.67$ or $67 \% $
Work Step by Step
Recall the basic principle of probabilities:
$P(\text{an event happens})=1-P(\text{an event does not happen})$
In our case, we have the probability of $33 \%=0.33$ that an American owns a cat. Thus, we simply subtract from $1$ to negate this probability:
$P(\text{does not own a cat})=1-P(\text{owns a cat})=1-0.33=0.67$ or $67\%$
