Now a US citizen and I have a life insurance policy in germany that has reached it's mature date and will pay out over 10,000 dollars, if I transfer to my US bank will I owe any taxes to the IRS?

Maybe. If the total of the premiums is LESS than $10,000, then the difference is taxable income.

It's not the transfer that's taxable, but the distribution of the money itself (if it's taxable, see previous answer). It wouldn't matter where in the world the money is.