Population growth is a net positive for economic growth. More people means more food required- stimulative, more housing required, etc. If you look at countries with small or negative population growth such as Japan, there are fewer people working and paying taxes to support the increasing number of older people who are retiring. This is also why immigration is a net positive for countries, the workers are taking low paying jobs, that would require higher wages for the native population. This translates into lower food prices in the US, as well as, higher profits for the business owner.
I hope that this if helpful.