Global mobile researcher and retirement pension

Dear All,

I am a European researcher and I will soon start a postdoc in the US (Minnesota).
I have a question regarding retirement pension for researchers abroad and global mobility.
As long as you work in Europe as European citizen, the process is quite simple. You collect all your payslips and your retirement pension is calculated and paid by your European host country.

My question is, what is the situation when you work outside Europe?
What is the situation for foreigners in the US? If you are currently a researcher in US or have worked there, can you please describe your situation and if you have an additional private retirement plan?

Comments and remarks from other alumni from other parts of the world are also welcome. Do some of you have a complementary retirement plan that can be used all around the world when you have an international job like researcher? For example,  you work in Luxembourg, than France, move to US than Australia,…

Thank you in advance for your further responses and for your help.

Sincerely,

FG