The skybridge would be required to be made accessible in the USA, regardless of whether its public or private. There are very limited exceptions to ADA requirements - the second the private company spent money “modernizing” a station without installing accessibility aids, they’d have opened themselves up to a lawsuit to compel them to make the station accessible.

I would imagine that Germany is no different that a lot of Western European countries in thinking it is better than the US (because it IS in a lot of ways). Would “we treat the disabled worse than Americans do” effectively trigger German national ego toward change? So long as you keep the convo focused on accessibility and not universal healthcare ;)