I earn $22000 per year working as an electrical engineer in control systems. Americans don't know how good they have it.
The term “six digits” as an aspirational salary goes at least as far back and 1959, but then it was more like “millionaire”. Still in the 80’s when it became popular as successful upper-middle class professional - 100k in 1983 would be $336,330 today.
$100k today would be 29,712 in 1983 when the median income was $24,580.