The US can do whatever it wants with its borders.  No-one is arguing that it can't.

However, by lumping in the 99.999% of Muslims who are moderate with the .001% who are radical, it is simply creating more radicals.

The effect of the ban is exactly the opposite of what is intended and will create more terrorists.  Even most Republicans know that.  Only people who live in the the Fox "News" Breitbart alternative fact universe think that it is a good idea.