Hey guess what? Immigration is not now, nor has it ever been, "destroying America." The mewling of the ignorant, cowardly, and weak notwithstanding, immigration is as inherent and vital an aspect of the character and identity of America today as it has always been.
Needless to say, anyone who can't or won't understand this simply doesn't understand America, the principles upon which it was founded, or what this greatest nation continues to stand for. Anyone fitting this description can't really - in the politico-philosophical sense - be considered an American, regardless of their citizenship or place of birth.
Anyone who buys into this ludicrous notion, has no conception of the simple geographic principles of population control that all nations employ, to protect themselves from the harms of immigration, as noted in the OP. As geographers around the worlds teach (including me 40 years ago), immigration laws are devised for this purpose. So that nations won't exceed their carrying capacity, thereby damaging themselves.
In the case of the USA, it's optimum population (relative to resource base) was passed in 1860 (at 30 million). If we had done as Canada (with a size & resource base about equiv, to us) has done (ie. keep population to a slim 30 million), then like Canada, who has a surplus of oil, we could/would be EXporting oil, and selling it for big bucks$$$ to bolster our finances. Instead we don't get to do that and our finances are $17 trillion in debt, while we IMport 70% of our oil.
And from what country do we buy more oil than any other country ? >> Canada.
Of course all this is just ONE facet of the overall Harms of Immigration list >>
Harms of Immigration
1. Americans lose jobs. (especially Whites due to affirmative action).
2. Wage reduction.
3. Tax $ lost (due to off books work + lower wages paid).
4. Remittance $$$ lost. ($40 Billion year).
5. Tax $$ lost to immigrants on welfare.
6. Increased crime.
7. Increased traffic congestion.
8. Increased pollution.
9. Overcrowding in hospital ERs.
10. Overcrowding in recreational facilities.
11. Overcrowding in government offices.
12. Overcrowding in schools.
13. Decrease in funds available for entitlements.
14. Cultural erosion.
15. Overuse of scarce resources (oil, gasoline, fresh water, jobs, electricity, food, etc)
16. Introduction of foreign diseases.