In USA what percent of expenses for roads and other transportation expenses are paid for by taxing gas?

Answer 1

Greetings!
it really doesn't matter because the tax money like the social security tax goes into the general fund. When any tax is made which is not dedicated then the government is free to do what they will and spend it as they like.
So when you hear or experience roads in disrepair and social security being broke, then remember it is because the politicians refuse to pass a dedicated tax.

Good Luck