So, which of the Israelites did God choose to heal of the snake bites when they were in the wilderness? - Those who looked upon the bronze serpent.

And which of the Israelites were called and given the offer to look upon the serpent and be healed? - All of them.

God sovereignly chose a method of salvation for the Israelites that clearly involved a condition to be met. Jesus, connects the events of the Bronze Serpent and the process of salvation as an illustration of his death on the cross in John 3:14-15 and also in John 12:32. 

Just as Mathew 22:14 says: “Many are called but few are chosen”. The gospel is offered to all, but God choses to regenerate (give new life) those who meet the conditions of repenting and turning to Jesus Christ as Lord.

It is important to not confuse faith as the source of salvation but rather as the condition in which God has decreed for whom he will save. God is the source.

If we look at the Jews in the wilderness that God gave the command of looking at the bronze serpent - the act of looking at the bronze serpent had no saving power in of itself. If a Jew would say, "I have gazed upon the bronze serpent - thus, I have saved myself" would be in grave error. The Jews did no work of their own regeneration as the bronze serpent was not the source of the power but was rather just a man-made tool that God used. For God did 100% of the regeneration to heal those bitten by the snakes in accordance with his condition of saving those who looked upon the serpent. The bronze serpent eventually became an Idol to the Jews and was destroyed by Hezekiah because the Jews were worshiping it instead of God.

A person today with a disease would NOT be healed in any capacity by finding a bronze serpent on a pole to look at or even if they were to reconstruct the original one and look at that. For the bronze serpent isn't the source of the power, God is.

Similarly, those of us who have Faith in Jesus Christ have done no work to save ourselves. Without Christ dying on the Cross, and being raised on the third day, having Faith in Christ would be of no effect, even Paul says: "And if Christ has not been raised, your faith is futile and you are still in your sins" (1 Corinthians 15:17). For we do not wield faith as a tool to save ourselves, but rather, Faith in Jesus Christ is the condition in which God has sovereignly decreed as the deciding factor as to whom he will elect to regenerate and in which he does 100% of the regeneration. Faith is Futile without God's decree behind it. This is why people's Faith in false gods leads to death. They are not a little more saved than an atheist, or partially saved, or 0.0001% closer to God because of their faith in other things. Faith in and of itself is not a source of power - which is what makes the Gospel so glorious. God's condition of salvation is not dependent on any work but is dependent on something of us that we can attach no power to because of how inherently powerless the act is. We only see Faith as powerful because of the Promise God has attached to Faith in Jesus Christ.

1 Corinthians 15:14-20
14 And if Christ has not been raised, then our preaching is in vain and your faith is in vain. 15 We are even found to be misrepresenting God, because we testified about God that he raised Christ, whom he did not raise if it is true that the dead are not raised. 16 For if the dead are not raised, not even Christ has been raised. 17 And if Christ has not been raised, your faith is futile and you are still in your sins. 18 Then those also who have fallen asleep in Christ have perished. 19 If in Christ we have hope[a] in this life only, we are of all people most to be pitied.

20 But in fact Christ has been raised from the dead, the firstfruits of those who have fallen asleep.

The doctrine of Unconditional Election makes no sense when contrasted by the words that Jesus and the Apostles spoke when they discuss the condition of faith to have eternal life. Believe in the Lord Jesus Christ and you shall be saved!

This process is sometimes called… you know… the Gospel.

When people say that regeneration is unconditional, or that regeneration precedes faith, they are removing a key component of the Gospel that has the potential to lead people astray in many ways.