President Andrew Jackson, whose picture hangs by Trump's desk in the Oval Office, defied the Supreme Court twice. When the Court said he couldn't slaughter or relocate the Cherokee Indians with the Trail of Tears, he said words to the effect of, "Supreme Court Chief Justice Marshall has made his ruling. Let him enforce it." When the Court ruled that he couldn't shut down the Second Bank of the United States, he simply went ahead and did it. Donald Trump may well follow Jackson's example, even if the Democrats in the House of Representatives appeal his obstruction of their impeachment inquiry to the Supreme Court and win. Democrats, and Americans more generally, need to get ready to deal with a completely lawless administration.
If this is how Trump plays this out, then they're indeed has been a coup. But it will have been a coup by the president and his cronies, not by Congress or the Democrats.