Hello!
Firstly, I must point out that our government is secular, meaning that government is ideally not affiliated, according to the secular theology, with religion. That being said, when Trump was inaugurated there were many mentions of the Bible and God, and he rules "according to Christian beliefs." (Though in reality, the things he advocates for go against the Christian religion). Since our government is secular, there would be theoretically no change if the majority of the population were to identify as Muslim. As for your questions about Constitution, since the very nature of our laws and actions must remain constitutional, it would be impossible for the Supreme Court (no matter who was on it) to rescind the Constitution, as that action itself would be unconstitional. The current President has already signed several executive orders which have been deemed unconstitutional, and lied to us (about something as petty as crowd size) on his first day of office. I am more worried about this Christian president than I am worried about Muslims. (Though I am not at all worried about Muslims). Now, you might ask: Isn't Isis Muslim? Well, yes and no. Yes they identify as Muslim, but they do not follow any of the Muslim ideology or laws outlined in the Qur'an. The things they do are glaringly anti-Muslim. Just like the things our President does are glaringly anti-Christian. Since they don't religiously follow the Muslim religion, it is not that which has made them into hateful terrorists. Therefore, I do not think of Isis as a group of Muslim terrorists. In fact, you should never typify a group/religion/race of people as predominantly terrorists just because a fractionally minuscule amount of them have committed these hateful acts. Nobody has ever typified European Christians as torturers or terrorists, even though they most definitely did this in "the name of God" during the early modern era, when conquistadors/explorers from Spain forced an entire foreign population to convert to Christianity, with the threat of torture and death if they disobeyed. These conquistadors' actions do not match the word of God, and these people do not represent the Christian religion. Therefore we don't classify all Christians as terrorists and torturers because of the influence of their religion, because we know this is not true and it would be idiotic to classify an entire race/religion as such. Muslims should be treated the same way.
From the content of your original post, I think you are asking more than a hypothetical question that relates to our government's organization.
Christianity, Judaism, and Islam are sister religions. If you take a look back in history, they all originated in a similar way and in accordance to each other's influence. They all teach those who follow it to be kind and to love a single, monotheistic God.
I would like to know why you wish for Muslims to stop growing in numbers. Firstly, the average amount of children per Muslim family is about 3, not 8. Secondly, shouldn't all religions be granted to right to procreate as they please? I don't understand why you wish to discourage Muslims from being accepted in America, when their religion (apart from the sharia--though Christianity also has certain elements of patriarchy) preaches nothing but love and acceptance. So what if America is predominantly Muslim? I'm a happy Christian, and my happiness extends to everyone regardless of their religious affiliation, just like the Bible has taught me to. The separation of church and state was a smart decision and means that laws will not change because of what the majority of the population affiliates with religiously.
Anyways
Have a wonderful day! Much love to my fellow human