As America enters a new decade, progressives are stepping boldly into … the bra-burning feminism of the 1970s. Specifically, they’re trying to resurrect the Equal Rights Amendment, the radical feminist constitutional amendment the rest of us had long thought a dead issue.

If they manage to ratify — a dubious constitutional proposition — they could enshrine left-wing gender dogmas into the highest law of the land. This year, Virginia is expected to ratify the ERA, bringing the total number of states to have done so since its heyday in the ’70s to 38, the threshold needed for amending the Constitution.

The amendment’s language sounds unobjectionable enough: “Equality of rights under the law shall not be denied or abridged by the United States or by any state on account of sex.” But precisely because of its broad language, the amendment could open the gateway to all manner of constitutional claims most Americans reject.

American women are living the freest, most prosperous lives in human history. The Constitution protects their right to speak, worship, vote, bear arms and more. The female jobless rate is at a historic low, and women own the majority of wealth in the country, along with earning the lion’s share of higher degrees.

Women are perfectly capable of flexing political power: They make up the majority of voters in nearly every election. Sex discrimination is already forbidden under both federal and state laws, as well as by the Equal Protection Clause of the 14th Amendment. The ERA won’t add to those protections, but could be used to impose sex-sameness.

Men and women are different physically, psychologically and emotionally. And while often those differences aren’t relevant, sometimes they matter a great deal, including in situations where women’s safety can be placed at risk if they are treated exactly like men.

Proponents deny that it would have radical effects. But the broadness of its language and the addition of the amendment to existing antidiscrimination laws could be used by radicals to force women to be drafted into combat, disallow separate-sex bathrooms or even pull government funding from ­women’s shelters. In New Mexico and Connecticut, state-level ERAs have been interpreted as requiring government funding for abortion.

The ERA could also threaten laws that don’t explicitly distinguish between men and women but provide benefits to stay-at-home wives or young mothers. For example, a non-working spouse’s ability to draw on Social Security or even grants encouraging girls’ participation in scientific fields could all perversely be treated as barriers to “equality.”

Then, too, today the meaning of “sex” is far from clear. In the hands of the right liberal judge, the ERA could become another weapon against women-only spaces and religious liberty, if “women” is interpreted to include men who subjectively claim to be female.

While many still think about the ERA as a relic of history, the amendment will be a live issue going into 2020. ERA proponents claim that they can combine recent ratifications in Nevada and Illinois with those from the 1970s. Yes, Congress imposed a deadline of 1982 for getting the required two-thirds approval back when it sent the proposed amendment to the states in the ’70s. But proponents claim that, once Virginia ratifies, all they need is a bare majority in the House and Senate to undo that deadline.

Courts have ruled that amendments must be ratified in a reasonable time frame, but the 27th amendment was ratified more than two centuries after James Madison proposed it. Can activists get around the old congression deadlines? And what of the fact that some of the ’70s ratifications have since been rescinded or had long-expired sunset clauses?

While opponents can no doubt marshal strong arguments against this unusual process for amending our highest law, many of these legal questions have never been confronted in the history of our republic. ERA opponents shouldn’t rely on the Supreme Court to bail them out if the ERA is “ratified.”

The Democratic House already held a hearing in April, and because Republican Senators Lisa Murkowski and Susan Collins are already on record supporting the ERA, stopping it in the Republican-controlled Senate is far from assured.

Which is why opponents must prepare to argue on the substance: Men and women are already equal under American law, but they aren’t the same. And that’s as it should be.