You've already noted that home insurance is requiremed by the mortgage company (who loaned you the money), not the federal government.
Flood insurance is similar: they can't loan you the money for a property in a flood zone unless you have flood insurance. In this case the "can't" is correct: a federally-regulated institution has to require the insurance. In this case, this is federal regulation of a bank, which insures depositors against failure.
All of the other examples are state-mandated -- not federally mandated. There's a big difference.
Finally, the federal "mandates" for the 55 speed limit and seat belt laws (as well as the age limit for purchasing alcohol) were all imposed the same way: Change your laws, or we will withhold your share of federal gas tax funds that we collected. A state could refuse those funds, on principle... but none did.
Some states took the money and posted the signs but refused to enforce the 55 limit. I think Montana was one of them.