America's economy is going down... what is the reason?

well the economy has never been the most stable thing in the world. much of it is the unaffordable loans that people took to buy cars, houses, etc. Many banks had took risky loans to people who could possibly not afford it with adjustable rates. The banks lost a lot of money when people who took loans to buy a house just forfeited the house and walked away when their rates skyrocketed for houses that they couldnt maintain. This caused a trickle effect in which the value of houses dropped. This meant that people who bought a house for 500k is now maybe worth 400k. However, the owners still paid a loan for 500k, but their market value is 400k, resulting in many people giving up their houses i dont believe that US's power is decreases, i think theyve been actually becoming more powerful and aggressive. like in WWII, theyve awaken the sleeping giant