>Our founding credo is that everyone belongs here.
This is an absurd falsehood. It is an indefensible assertion based on nothing but modern moralism.
>We are the wealthiest country in the world
This wealth can be squandered by catering to the desires of outsiders that want to come here. We should stand behind maintaining that wealth, power, and quality of life for our dependents and pass along that prosperity to them.
Turning the country from 96% literate to 79%, and all the associated degradation that comes along with that, is not the morally honorable position. The demographics in 1980, let alone 1776 were very specific and narrow.
I'll note that no one supporting this seems to be claiming the country will be better or stronger or this will benefit the citizens already here. Only that it is good for the people coming in. This is not how politics is done well or national interest is defended. Leaders that pursue this are abdicating their responsibility towards the people they are supposed to serve.