Elon Musk is a very, very smart man. And, he is unequivocally correct that the Democratic Party would love nothing more than to create a one party government in America as they have done in California. There my agreement begins to waver. Although he is an American born in another place and more American than many Americans I know, I suspect that his reasoning is influenced by some of the instincts that he may have inherited being born in South Africa and he didn't arrive in America until California was well on its way to becoming a one party state. I have the advantage of living in California and witnessing the transition. Illegal aliens didn't play a role in that transition. Nor, IMHO, will they in any future transition.
Illegal aliens have been induced to migrate to America with promises of wealth that America can't provide. For as rich as we may appear to the poor, America simply isn't that wealthy. Indeed, America has no wealth whatsoever. It's government has none either. Wealth is a very fragile commodity renewed day by day by the labors of its citizens. Importing subjects and forcing citizens to share their wealth with these aliens has two effects. First, it dilutes the available wealth. Second it disincentivizes the wealth creators. Thus, America will cease to exist before any party can take power over it.