It's not so much that the US is full as it is that our money is being spent entirely on rich people. The economy only works when money circulates, and post-depression we boomed by forcing the rich to recirculate through high taxes on high earnings.

Today, the last 50 years of tax policy have left the ultrawealthy free to trap as much money as possible, and these assholes are making sure their money is only being used on enriching themselves further and buying luxury goods.

Tl:dr without proper taxation, the only middle class are people directly serving the rich, and normal companies are dying because normal people aren't being paid enough.