In the US I can quit a job with 0 days notice. I can also be fired from a job with 0 days notice and no severance.
That makes the job market significantly more fluid. If there is demand for a specific job compensation will go up quickly as there is no artificial buffer on people switching jobs for better pay. Supply and demand is very sensitive to small shifts in either. Companies are also not afraid of paying this compensation since worst case they'll just do some layoffs.
If a US company has some employees in Europe then they still have a benefit from all this so they can pay more than a purely European company. If they need to cut costs they can fire the expensive US employees first and then adjust the Europe comp more slowly. If they need to grow quickly they can do so in the US and then slowly shift to Europe.
edit: The profit margins of US tech companies are also massive as they have relatively little regulation, taxes or bureaucracy. Goggle makes $2 MILLION/employee/year. So no risk of not making record profits by paying an extra $200k.
I mean as someone who has experienced both the US and Europe I would say this applies to most everyone posting here.
And if we're going to sling insults then I'll say it's hilariously amusing how clearly fragile the egos of the people posting here are.