Almighty God is just and fair. He does not punish one person for the sins of someone else. As Allah says in the Qur'an:
Wa Laa Taziru Waaziratun Wizra Ukhraa.
Non-Muslims will answer to Allah for all the things they did wrong or did not do right. Including how seriously they did or did not search for Truth about God.
And how open- or closed-minded they were when Truth came to them from someone else, such as, for example, a Muslim who wanted to reach out to them and give them Islam.
Muslims will answer for their own acts of commission as well as omission of all kinds, including how seriously they tried to take the Message of Islam to every Non-Muslim man and woman they possibly could.
Neither side will be faulted or held responsible for the failures or excesses of the other side.
For, they both have the same God, God Almighty, and he is a fair and just God. And he does not punish one human being for the sins of another human being.