Why Does America Keep Drifting Left?

Because it is a degenerate matriarchy.

The West became a degenerate matriarchy when men no longer had to be marriageable to have sex from moral and rational women.

Most Western men have no intention or prospect of marriage and most Western women do not want to marry until they are themselves no longer marriageable.

There are basically not enough marriageable men prepared to risk anything to restore the patriarchy. This means that the West will continue on its trajectory of death by a thousand cuts in their degenerate matriarchy while they will see, smell and hear their civilisation putrefy before their eyes.

The left have attractive women which attracts higher quality and higher status men. The right only have unmarriageable bachelors abandoned by their fathers suffering from Dunning-Kruger.

"The left have been able to seize the high ground"? Actually, infantilised senior women in public life prefer woke beliefs and unprincipled senior men who are atheists and nihilists submit to them. Lower status men take their cue from higher status men and join them in the submission to the degenerate matriarchy after having their faces forced into the moral sewage of the matriarchy by their lack of anything resembling principle because they lack a functioning  moral system ie religion.