Those laws are different in each state, and of course there will be slightly different interpretations of the laws in some local jurisdictions. Here is a link for a website where you can view a .pdf file listing the tint limits for all states:
www.iwfa.com/iwfa/Consumer_Info/auto_statelaws.html This is almost a 2 megabyte file, in case you dont have broadand internet access, and takes a while to download.
The chart doesnt list all of the related complexities of the laws in all states either; for example, what if you add tint to a window whose glass already has the slight tint as it came from the factory? Most states would measure the total % of tint - though not all.
Im sure there is more info if you start from the IWFA home page:
www.iwfa.com/
I did a google search for +window +tint +states. There were plenty of sites, and not all of them had the same information, i.e. they may not be current, or may be wrong. The TX limits were apparently updated in 2003, and changed somewhat from previous values.
Then there is the question of whether you could get a ticket in another state for window tint, even though you were compliant in the state where your car is registered. The reciprocity laws for this stuff also vary from state to state.