Extreme progressives would destabilize the country by setting up structural racism and sexism in order to achieve "equity", dissolving borders, gutting the police, and over taxing companies.
Extreme rightists would destabilize the country by repealing too much of the social safety net, closing down the country to immigrants, militarizing the police, and letting companies behave anti-socially with no repercussions.
Our enemies are smart to try to push us into embracing extreme policies. Either way they win. Because when our institutions start to fail we won't be able to project power anymore. It will draw us off of the world stage to some extent.