"why is it trump's fault"
In a big way it is.
If I was a potential parent, I wouldn't want any child of mine growing up under a dictatorship.
A temporary decline in population growth in the USA is a dead giveaway of how people feel about Trump and his plans for an autocracy.
Once a Democrat is in charge and faith in the US government is restored, things will go back to normal.
All anybody has to do is vote for it.
IMO, the brains of all of them, including Trump, reside below the belt buckle.