It is a joke.
Kamela represents the state of Kalifornia. The state has declared that Iowa is a state non grata as far as Kalifornia is concerned. So while Kamela is legally permitted to visit any state in the union, she will be doing so contrary to the express wishes of the entire state government and presumably the people of Kalifornia.
There are no good outcomes here for Kamela.
If you think that tweet affects anyone besides Ted Cruz you should put the bottle down.
It will not affect Harris at all, nor her prospects in the race. Nor will it affect the State of California.
She and the State are already destined to failure.