The way to do it is with quotas. 100,000 vehicles per year per manufacturer with a country cap of 10% of previous year’s total passenger-vehicle sales (the latter currently 15+ million in America).
Then you slowly ramp up those limits over time to e.g. 200,000 and 20%. Enough to give consumers respite and producers a taste of the true competition. But not so much of a shock as to cause a mass extinction.