The effect of unionization had the opposite effect in Germany, Denmark, etc. It caused a huge shift to contract work. Contractors have more protections in those countries than they do here, but do not enjoy nearly the same protections as full time employees.
http://ec.europa.eu/epsc/publications/strategic-notes/future...
https://www.nytimes.com/2017/12/11/business/europe-labor-rig...
I admit that the social protections in those countries generally means that the shift to contractor work is less likely to affect things like cost of healthcare, retirement, etc.
Some big US tech companies might be zombies (IBM, HP), but with our less restrictive labor laws and emphasis on entrepreneurship they have been replaced with new giants (Google, Facebook, etc.)
This did not happen in the tech sector in Europe, the giants fell, Bull, Nokia, etc. and nothing rose up to their size outside of the banking sector. Part of the reason may have been that the overall environment was not flexible enough to allow new entrants, among many other factors. SAP remains strong, but I can't think of another pure software/IT company in Europe of that size or market position.