You and I have hashed out Romans 1 and Ephesians 4 and Acts 10 several times. And this is relating to your post I have quoted. I believe it is reasonable to say from those Verse references that God does indeed manifest Himself to all humans to say from Creation to Hearing the Gospel to whatever it may be I God is real.God has always proclaimed that He will have mercy only on those of His choosing. But, as I can see, you believe that He must be an equal opportunity Savior for all mankind. If He does not save all, then He is unfair in your eyes.
In that case, the entire Bible should be re-written because it is crystal clear that He chose Israel, and utterly destroyed other nations!
Now, to go along with your post I would add that for some people God is vague about making Himself known and to others He makes sure without a doubt they know He is God.
And the difference is remarkable and very distinguishing.