Is it true that Americans are living "paycheck to paycheck"?


(paycheck to paycheck, 形容这个月工资花完了盼着下一个月的工资单过日子。)

I've been seeing online a lot of commentators saying that American citizens are living "paycheck to paycheck" and made me wonder how is it possible considering the USA is still #1 or very possibly #2 economic power in the World after China?
I am from Serbia and love my country but due to low pays here made me want to move to the US at the time. When I was younger all I've seen on media is that Americans live pretty comfortable lives with no major economic issues.
So average American citizens, is there any truth to the claim that Americans are living "paycheck to paycheck" and that the US economy and life are not that perfect?