Churches provide services to communities far exceeding 70 billion. Trying to judge churches on what some fringe groups and politicians do is short-sighted.
The American protestant churches are to Christianity what the Society of Saint Pius X is to the Roman Catholic Church and it's a big enough group of people that it can stand judgement on its own.
As for the services churches provide - the whole point of taxes is pooling capital that the government can use to more efficiently provide far better services to its constituents than any non-governmental organization can. If the churches were actually capable of providing those services beyond largely superficial displays of charity and piety, we wouldn't need government to begin with.
To me it seems that both churches and military investment (in the very broad) are essential and integral for the stability of the US.
I think whether this should be changed is debatable, however I don't think this can be done over night, as it would destroy said stability. Even if a majority could be gained for such a project I think it would have to be a very slow process, as so many other things are built on this foundation and many things seem to have been optimized for this system over time.
However, I am not an expert by any means and just rely on what I see, hear and think when I compare it with Europe. The only thing I have learned is that telling people to do it like others isn't something that can just be done - while keeping some stability that is.
Nah.