Hi and welcome to our site!From US tax prospective - contributions into your Switzerland retirement account are not deductible - thus while such contributions do not reduce your US taxable income. Only contributions into US qualified retirement accounts may be deducted.Thus - from US tax prospective - your contributions into foreign retirement account will be your basis(investment in the contract).When distributed - just as with domestic pensions or annuities, the taxable amount generally is the Gross Distribution minus the basis.
The Swiss Social Security taxes are not reimbursed if you leave the country - but under some circumstances - you might be eligible to receive social security benefits.You will find some additional information in THIS PUBLICATION.A private pension generally available when you are no longer employed. However there might be vesting schedule and additional limitations set by your employer. None of private pensions are the same. I suggest to contact HR person in your company who is responsible for employee benefits and ask for the pamphlet which contains all information about your pension plan.