How is money created?
Re: "You could say this is 'creating' money" - no you couldn't. This would be conflating money and wealth. Wealth can be created without new money being created - indeed wealth was created before money even existed. Conversely money can be created without creating wealth. So they are entirely separate things. A crude analogy: wealth is to money as apples are to numbers. You can count apples using numbers, but growing new apples does not create new numbers.

With regard "In the end logically, this money becomes concentrated in a few people." - not true. People don't earn money in order to collect big piles of it and spend all day counting it. Instead they use it to buy stuff which means that the money circulates through the rest of the economy.

With regard "How is it the United States can still grow, despite sending more money out than it takes in?"... it doesn't send out more money than in takes in (at least not to any great extent). Foreigners do not accumulate great piles of dollars that they earned from selling American's stuff - instead they use their dollars to buy American assets, like US government bonds.

With regard how money is created, please be aware that this is a controversial area and there is a huge amount of misinformation on this subject. The best document to read that I know of on the subject of money creation is this one published in the Bank of England Quarterly bulletin in 2014.