The weapons technology in question is completely different. Fast, precision strikes are more effective against factions, individuals, etc. Assuming these would be strategically positioned around the world, the US military could theoretically destroy a city block or an individual building within 15 minutes of targeting or faster. That's a waayyyyy more effective tool to ensure you maintain control. If you can kill individuals that lead your enemies while leaving all of their resources (human included) intact, nuclear weapons aren't so appealing anymore. Why destroy a city when you can just kill your enemies and leave the city mostly intact? War is changing. Speed and precision > brute force.