I can’t believe anyone would seriously propose one of those “responsible backdoor” schemes.
You either have to be super old school and not understand basic principles of computing/information exchange (similar to former US senator Ted Stevens talking about “an internet” [email] being sent by his staff) or be super naive (or maybe malicious).
A “responsible backdoor” scheme would mean that communications using US services/products could be intercepted by anyone (from script kiddies and obsessive former partners to Russian/Chinese intel) and that all secured/business communications/systems would run on non-American products (open or closed source). If anything, such an idea would be a death knell for the US software industry. No sane company would run services/products that can be broken even by low tier hackers.
You could argue that the US gov. would be able to secure access to their “golden keys;” but I don’t buy that. Such a scheme would be massively complex (bigger attack surface) and both Russia and China would dedicate significant resources to figure out a way to break it.