Yes but so is a lot of Christian nationalism yet here we ars

Sharia law is "eye for an eye" based, similar enough to Christo fascist agenda on sexuality and (female) modesty. There are no constitutional protections for inter faith/race/gender marriage/sex, modesty, and deeply religious (christo fascist bias to constitution) judges can be appointed in greater numbers. For contract law, sharia rules are permitted for financing/marriage (divorce) in the US, but obviously non-sharia contracts are permitted too. There are no constitutional protections against prenups, or contracts that include "don't be evil" covenants.

Typically, Sharia objections come from liberalism. Not the specific biblical verse that imposes morality/hierarchical control laws. Opponent to this guy should just say "he wants trans sluts walking around in mini skirts and lipstick, and always believed in their accusations against men"

the constitution is the law of the land, to have any other law you would need to fully overthrow the government. within the US sharia law is just the inner workings of any Muslim faith when dealing with themselves or how they chose to deal with others. every religion and many groups do this. Mormons have Bishop's Court where they have local leaders meet with people who will decide if they will excommunicate someone for a particular sin or behavior like adultery or abuse, they may also use these formal proceedings to decide if the church itself will recognize a divorce or annulmemt within their own religion, the US government isn't involved in or forbidding Mormons from running these 'Mormon court of law' proceedings as everyone involved is legally free to not even give a shit or participate if they don't want to and it effectivly means nothing to anyone outside their church groups if it even means much inside those groups. but at one point the US government did go to war with the Mormon Church to stop them from taking over the country or some other fever dream because it was a good distraction from the upcoming civil war, and at some point Mormons were a huge voting bloc moving into areas and taking them over and electing their leaders into the highest offices they could and clearly they intended to become the dominate culture and religion of the US from the top down for a good while, but if a whole political party was constantly going off on how we need to ban Mormon Law before it takes over the country, you'd be right to laugh at them.