What should be the target population of the U.S. and the world?

I think we're fine on where we're at. Now, I do believe in more wealth distribution since the U.S. holds the most richest humans on the planet, yet still has over a million who are homeless and millions more who are struggling in the same country. If not wealth, the government could at least put a bigger effort in ensuring these individuals have basic needs (food, water, clothes, warmth, shelter) rather than leaving it all up to local volunteers.

What makes you believe we should have more people?

The planet can't support that many people.

This has to be a dumbass troll attempt. There's already too many at 7B.