A. It is impossible to believe the Gospel unless God causes you to believe.
Yes, God grants faith;
Romans 12:3, and yet not all have faith;
2 Thessalonians 3:2. That's the facts, Jack.
B. I am responsible for not believing the Gospel.
An unbeliever is already on his or her way to hell prior to ever hearing the Gospel, and, some have never heard the Gospel. That being said, you need to hear the Gospel, and it isn't of works. Mankind is held responsible for their sins, and for not repenting of their sins. God is just in commanding all to do this, even if his call is only effectual to his chosen.
But I digress, I don't see God as having to fit into my idea of fairness, nor do I think Wholly Other to be such a God that he must succumb to my whims and checklist of God criteria to be God. This isn't idolatry or Burger King, we're talking about an eternal being who is way above our thoughts. He is who he has revealed himself to be, he's actually
God.
C. Therefore I am responsible for not being able to do the impossible.
See, there you go. The flesh profits nothing concerning salvation;
John 6:63. You want it to, you believe it does but it doesn't. You see salvation and saving yourself as something in your hands, and if not, well really,
since not, you deem God as unfair;
Romans 9:20.
You see the Gospel as something you can do, which is why you arrive in the end at a works gospel.
Furthermore, all persons are responsible for their sins, regardless of believing the Gospel and being converted, and are already under condemnation;
John 3:17. God, being Sovereign has mercy upon whom he wills to have mercy;
Romans 9:14-18, none can come to Christ unless granted by the Father;
John 6:44.
That's the Gospel, and frankly, it ought to scare the hell out of people, literally, when they see
all it's glorious truths especially when they see the salvation of their souls are solely in God's hands. All his elect will run to him for mercy and grace, all the lost will continue to hate him for eternity.