The states lost this battle (South Dakota v. Dole). Perhaps the feds may not be able to directly set speed limits, drinking ages, BAL drunk driving thresholds, etc., but they can conditional federal highway money on such things via Congressional spending power.

This played out again recently with the 0.08 BAL threshold for DUI demanded by Congress. There was a Wall Street Journal article on how Louisiana resisted this as long as it could, but finally relented. Federal highway money is just too substantial and necessary for a state to pass it up.

Regarding speed limits, I believe that Congress reversed course and allowed states to set their own.