[Big Dave]

The Europeans have different roads and cities so they'll do as they will.

US manufacturers face different realities.

Legacy costs mean a US manufacturer has to charge $25,000 minimum and more like $35,000 per unit of they are just trading dollars. No real profit.

US crash test standards mean a tandem car sold in the US is going to have to weigh at least 2,500 lb or be made of something like carbon fiber.

I don't think the US consumer is going to want to cough up more than $15,000 on what most will see as a glorified motorcycle unless gas prices get truly outrageous. Honda does sell $21,000 Gold Wings in the US but to a niche market and to continue making a quality product they had to move Gold Wing production out of Ohio and back to Japan. But that currently defines the top end of the tandem seating market in the US today.

40 CFR 63 pretty much rules out small-batch hand layup auto production. to meet that reg, you need some sort of SMC with a 400 ton curing press, vacuum venting and a gas-fired afterburner. Not a game for the financially faint of heart.

I think there is a market for a tandem-seat car for the long-distance (relatively) high speed commuter. There are a lot of such people out there. The job market is tight and the real estate market in the US militates against moving to the job, particularly when jobs are no longer careers but gigs.

A tandem-seat 1+1 with a small diesel (it better have a Cummins badge on it to sell in the US) with a paddle-shifted dual clutch 8 speed, 4x2, with a decent HVAC system could sell if you keep it under $15,000. Could you make it profitably? Would it comply with all applicable requirements?

Questionable.