Is it ever acceptable to have pedestrian or cyclist deaths to have buses, trains, ambulances, fire trucks?

What a strange question. The answer is of course 'rather not'. But those are for the most part unavoidable without society paying a (potentially) much higher price. So we have decided to accept those risks.

In this case it is another country trying to impose their 'way of life' on the rest of the world, or in this case, the EU, which has a different set of values.

That doesn't really have anything to do with having buses or trains vs cyclists, it is not a personal decision and there are many alternatives compared to US vehicles that were never designed for European (or Asian, for that matter) traffic in the first place. The USA is very car centric to the point that walking is frowned upon (I got picked up by the police in North Dakota for walking). The EU is simply not like that, and that's fine. The USA should set their own standards for car safety and so should the EU, if that leads to incompatible products I think the mantra is 'let the market sort it out'. The Japanese seem to have figured out how to make vehicles for different markets, there is no reason the USA can not do the same thing.

Buses and trains decrease the number of cars on the road by pooling travellers. Ambulances and fire trucks serve a purpose beyond making individuals travel comfortably. This is a straw man.