Welfare organisations in non-islamic states usually have in their statutes that they help independently from religion. The help is often not directed to a particular but to a community. Christians often pay tithe (the Jewish and Christian equivalent to zakat) through such organisations. Some of the persons helped are Muslim, some are not, and there are usually more Muslims recieving help than Muslims who contribute.
Can/should this kind of help be considered as zakat or is it to be considered sadaqah?
In this context, see also
Mixed-religion states usually do have not separate rulings and separate accounts per religion.
According to traditional fiqh, zakat is payed inside the Umma
(Note The answer in Is it Zakat, if you donate to different charity organizations? does not really hit the point because it refers to non-charity projects)