Now almost everything that used to be made in the US (west) is now made in the 3rd world, they simply closed all the factories in the west full of union workers and opened them in China or other countries
Why is that a problem?
US unemployment rate is around 4% which is a very healthy number. US GDP growth is at 2.8% last year which easily surpassed most developed country. People build factories in China didn't lead to huge amount of people losing jobs, they simply take other jobs in different industry, which makes more money than factories jobs.
US excels in IP design and tech services. Majority of their money came from that. If you look at top 100 market cap companies overwhelming majority of them are American companies. They don't need tons of factories to make money, they made far more money from being the one who contract those Chinese factories.
Note that I do think western countries needs to increase manufacturing industry %, but it isn't because western people need factory jobs, but because manufacturing industry increases a country's resilience during war. If majority of manufacturing are done in China or pro-China countries, it's like you have a hostage being held in an enemy territory. They can use this to punish you hardcore.
But this is a geopolitics strategy issue, not unions issue.
If China isn't so obviously anti-west, I think poor country doing manufacturing and first world country doing IP design related work is probably the best for the economy.