Jesus Christ provides the righteousness of God for our behalf because we can not match God's standards (and we receive the righteousness by faith -- accepting Jesus as Lord and Savior). From the salvation plan, there are pretty much no grounds for us to boast in ourselves (especially since we can't match God's standards on our own). Even with the Jews being aware of God's standards and having the Mosaic Law, the Jews can't boast in themselves either.
In fact, Paul declares that the God of the Jews is "also the God of the Gentiles" (3:29). Paul talks about how there is "one God" (3:30), and "one God" really means "one God" if it is universal (rather than a localized area).
So God is the one ultimate universal ruler, meaning that God's salvation plan is available for all people (not just Jews). Paul talks about how the one God "justif[ies] the circumcised by faith and the uncircumcised through faith" (3:30). God definitely has wide reach with the salvation plan -- and it also demonstrates his great love for every single human being!