Your decisions affect the lives of all the people living in this country.
It really depends on which people that make the decisions are being referred to and in what context.
For example is the sentence about politicians who make decisions on health or immigration status etc or is it about the decisions that ordinary people make every day about literally anything; this will change the sentence and how to construct it.
Although lives don't live? all languages have strange daily sayings that are used and understood even though they don't make a lot of grammatical dictionary definition sense.
Your sentence would be understood