H1Bs have been used as a path to citizenship for a long time. You can't just change the rules like that without destroying so many lives in a senseless act of cruelty. But the cruelty is the point.
* America was built by immigrants.
* None of the Americans currently alive "built this prosperous nation". They were born into it.
* Welcoming immigrants won't "kick Americans to the curb".
* There are Americans currently alive who are direct descendants of the pioneers and colonists who created this great nation who deserve to prosper from their ancestors' sacrifice(s)
* Resources (housing) and opportunities (jobs) are finite -- if Heritage Americans have to compete with the entire developing world for their birthright, there is a non-zero chance they will be "kicked to the curb" so to speak.
* I utterly reject the concept of "birthright". Birth alone does not entitle one to anything. You want prosperity? Work for it.
* Housing can be built, opportunities are created as the population grows. Immigration is economically beneficial to the country that harbors them.