Labor unions were very effective at increasing wages for blue collar jobs. Particularly ones not easily outsourced, like construction. Businesses have lobbied to systematically attack organized labor for around 100 years. The few unions left are relics from an earlier time. Businesses have made it neigh impossible to form new ones.
The "gig economy" is a new form of exploitation. Technology has enabled a new breed of job that barely skirts employee regulations. This has undone decades of worker protections.
Importation of foreign workers has been good for foreign workers, but in the US is mostly a tool to suppress wages. You can get away with more law breaking when your employees are wholly dependant on you. Job Visas are indentured servitude.
The US has regressed in every income inequality metric over the last 50 years. To out it simply, the ultra rich own half the country. You don't see this same wealth concentration happening in Europe.
If wages kept pace with worker productivity, the average worker would make something like $150,000 a year. The productivity gains are real, but all this money has gone to the people at the top. Tax law is just a small part of why the median American is getting poorer while the average American gets richer