That's a valid wish, but there is already a large number of people in America who oppose American values. So in principle there is no difference whether their number will grow by immigration, high birthrate, indoctrination of other peoples children, or adults changing their views.

So simply opposing immigration won't accomplish what you want, it will only be used as a weapon against you.

If you really want to keep your values, you need to find ways to attract more people who have the same values.

E.g. Cubans who run away have a good immunity against communism, that's why people who make it so easy to cross the border by foot, made it hard to enter by boats.