Where can I find online that a birth cert can no longer be used driving into Mex.?

When you go across the border, you p ONLY through the Mexican Authorities, correct? Has Mexico been instructed not to allow US Citizens into their country with only a birth cert and photo ID.....or are they retaliating to the US requirement. I understand that the US authorities will let you across back into the US with these docs if you show up in their worldly computer...........I would like to see where you can find the correct info out. Also, I understand that there is a card that substitutes for a pport or does it take a pport to get the card? Someone says you can have your drivers license fixed so it acts like this card. I understand that this is something you can get almost instantly or do you need to apply similarly like a pport and wait?