What happened is that the Democrat party abandoned liberal principles and embraced identity politics, instead. They don't have an actual platform these days, only a strategy for getting elected, and all the illegal aliens they are bringing in represent part of that strategy.
Once again a right winger tells us where Democrats "went wrong". Democrats didn't embrace "identity politics", Republicans started actively working to strip minorities of simple civic liberties.
There is a streak of Puritanism a mile wide in US politics. You keep trying to legislate a narrow and twisted version of "morality" that dubs anything you believe is "bad for people", but in reality imposes a Puritanical value on a certain way of life.
Prohibition was one such law. Pushed by the Women's Christian Temperance Union as a solution to poverty and abuse among the poor. It fueled lawlessness, bribery, smuggling, and mob violence. The unintended consequences of right wing puritanism run amok.
Now the right has gone crazy over the idea of "open borders, drugs and sex fueling the decline of "American Values". Republicans have intensified their attacks on public education, blaming them for various lies and bullshit from CRT and "grooming" their children for sexual abuse, and immorality.
Republicans can see no connection between closing the border for 2 years, and the rising price of food in the grocery stores. Without illegal immigrant labour, or even visa based immigrant labour, to plant the crops, harvest the crops, or process the crops, prices are rising. Instead of making the correlation between the lack of cheap illegal labour and the price of food, the billionaire owned right wing media is blaming Joe Biden for the rising prices.
And while Republicans play stupid politics, with non-issues like gay marriage, trans rights, and gun violence, the real issues of lack of access to medical care among the poor, income and wealth inequity, school shootings, the economic effects of unchecked climate change, and a whole range of other REAL issues, while they pursue their made up "American values", which never were.
Republicans have no solutions to any of these problems, other than keeping leadership in American white, living the life of evangelical Christian morals.