Colonization can really sneak up on you. For now Islam is still a distant second to Christianity, but when you’re importing large numbers of immigrants whose main form of income is producing welfare cases, it won’t stay that way for long.
Just look at Europe.
Islam here is characterized by the green states. Buddhism by the yellow and Judaism by the pink. As you can Hindus by the brown and Bahai’s by the teal. Apparently there are a whole lot of black Bahai in South Carolina.
At the county level though, you can see that Islam and most non-Christian religions are concentrated in specific areas.
Islam has sway in twenty states in the South and Midwest at the moment, but its real growth is likely to be in traditional urban areas. It will just take a bit longer to turn New York into Newyorkistan and it will be easier to see the numbers impact in places where Muslim settlers don’t have much demographic competition from non-Muslim immigrant groups.