That makes sense too, but I was looking at it from the other side - people know they need to rely on the churches for support in the US, so they stay with them so they have that support network in case of illness or disability. On the other hand in Europe people have felt free to leave churches because their taxes pay for that support.

In the UK, at least, there's even quite an anti-charity stance by a number of people, who consider it the State's role to, for example, provide foreign aid or fund cancer research, and condider donating directly to those causes to be encouraging the State to abrogate its responsibility.