Who under the Old Covenant?

Seems like some pretty important information to know, considering Hebrews 9:15 says that Jesus died to set THEM free from sins committed under the Old Covenant. 

In my understanding, only the ancient Hebrews / children of Israel were under that covenant, so it was THEIR sins that Jesus died for, NOT ours!

Which in my opinion makes alot more sense in light of these verses below which talk about God not counting sin against those who were not under Law, nor God counting sin against anyone since the cross... jmo, what's your thoughts? 

Romans 5:13 - To be sure, sin was in the world before the law was given, but sin is not charged against anyone’s account where there is no law.

Romans 4:15 -  because the law brings wrath. And where there is no law there is no transgression.

2 Corinthians 5:19 - that God was reconciling the world to himself in Christ, not counting people’s sins against them. And he has committed to us the message of reconciliation.

If these verses are accurate, then it's safe to say that Jesus didn't die for our since because none of us are 2,000 years old, nor have any of us been under that Old Covenant Law. 

Not to take glory away from what Jesus did do, but perhaps restore some of the glory to the Father and also help Christians see that they shouldn't judge unbelievers for perceived sins, when God Himself isn't judging them. 

Kinda nips that self-righteous crap right in the bud... as the saying goes.