If we have to use them, we surely will.
Do you know that America has a "mutual defence treaty" with the Philippines, yet they did not stop China from seizing the Scarborough shoal in 2012?
Apparently they believe that these weapons are not just for show, or they wouldn't have abandoned their ally.
Same story with Russia and Crimea. America promised to protect Ukraine's borders in 1994, in exchange for them giving up their nukes.
But when push came to shove in 2014, Americans realized that they did not want to fight a nuclear war with Russia over Crimea.
Mutually assured destruction only works when you believe the other side is willing to use their nukes. And apparently America believes it, so MAD still applies.
On the day they stop believing it, we may see some American troops trying to take back Crimea from Russia, and Scarborough shoal from China.