Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God.
Romans 3:19 ESV

This verse is written as a parallelism.

A> Whatever the law says
B>> It speaks to those who are under the Law
A> That every mouth may be stopped
B>> The whole world may be held accountable

The only way this verse makes sense is if the Law applies to all people on earth. "Those who are under the Law" = "The whole world", which must be held accountable.

Paul and John both define the sin as transgression of God's Law and "all have sinned", no matter into what nation they were born.

I can't reach any conclusion except the whole world--not just the Jews--is under the Law because they have broken it. Only when you repent of breaking the Law and beg God's forgiveness are you no longer under the Law.