with the exception of 2, God only brought the under 20 crowd out of the wilderness. They weren't held accountable .
You are incorrect in your statement. The reason God allowed the children to survive is because their fathers said that they would die in the wilderness. God proved them wrong. Please consider:
Deu 1:39 "Moreover, your little ones who you said would become a prey, and your sons, who this day have no knowledge of good or evil, shall enter there, and I will give it to them and they shall possess it."
Less you think the verse "have no knowledge of good or evil" shows an "age of accountability" please consider that God was going to wipe every one of them out and make a great nation of Moses. Please consider:
Exo 32:10 "Now then let Me alone, that My anger may burn against them and that I may destroy them; and I will make of you a great nation."
and again...
Num 16:21 "Separate yourselves from among this congregation, that I may consume them instantly."
And if you think God does not bring forth His wrath on children than consider this passage one of many...
Num 16:25-32 "Then Moses arose and went to Dathan and Abiram, with the elders of Israel following him, and he spoke to the congregation, saying, "Depart now from the tents of these wicked men, and touch nothing that belongs to them, or you will be swept away in all their sin." So they got back from around the dwellings of Korah, Dathan and Abiram; and Dathan and Abiram came out and stood at the doorway of their tents, along with their wives and their sons and their little ones. Moses said, "By this you shall know that the LORD has sent me to do all these deeds; for this is not my doing. "If these men die the death of all men or if they suffer the fate of all men, then the LORD has not sent me. "But if the LORD brings about an entirely new thing and the ground opens its mouth and swallows them up with all that is theirs, and they descend alive into Sheol, then you will understand that these men have spurned the LORD." As he finished speaking all these words, the ground that was under them split open; and the earth opened its mouth and swallowed them up, and their households, and all the men who belonged to Korah with their possessions.
There is no such thing as an "age of accountability".
So is everyone under 20 , under the age of accountability?