God withholding His mercy from some, and choosing to show it to others?
1) God has judicially blinded the nation of Israel, for the most part, specifically so that they cannot see, hear and believe on His Son in Matthew 13:10-17, Mark 4:10-12, John 12:37-40, Romans 11:7-11. This leaves them in their sins.
2) The Gospel is hid to them that believe not ( 2 Corinthians 4:3-4 ) by Satan because the Lord allows it. Again, this leaves all who are blinded by Satan in their sins, and does not show them His mercy.
3) In 2 Thessalonians 2, Paul tells the church at Thessalonica that when Anti-Christ comes, the Lord will send those who are not His people a strong delusion... so that they will believe the lie that Anti-Christ is God, and will voluntarily take the mark. This leaves them in their sins.
There are many other places in the Scriptures that objectively show the Lord choosing one and not another;
Choosing to blind some and not others, etc.
God has mercy upon whom He will have mercy ( Romans 9 ), Charlie.
If anyone has believed on His Son, it's because He chose to have mercy on them and to allow His Son to reveal the truth of who He really is, to their hearts and minds ( Matthew 11:25-27 ).
Have you not read of these things?
Of course I've read them, many times!
All three examples you gave and several more including Pharaoh in Exodus are examples of rebellion and hardened hearts against God.
God gives you what you want, as far as accepting Him or not. If you rebel and continue that rebellion and hardness against God He will give you a firm hardness against Him.
In Israel's case, God made a promise to Abraham that He will keep. God has blinded Israel and set them aside until the Church Age has run it's course, as Paul has clearly said. God is dealing separately with Israel's salvation that will come after the Church Age has come to its full.