Getting social welfare in a non-Muslim country is permissible as long as the person deserves it.
Responding to the question, Dr. Monzer Kahf, a prominent economist and counselor, states the following:
The money received as welfare in any country, Muslim or non-Muslim, is permissible in the Sharia provided you deserve it according to the law. It can be used for personal expenses, charity, building a Mosque, or any other purpose. The reason is that all governments, Muslim and non-Muslims alike, are permitted to give grants and assistance to people as long as such giving serves the public interest as defined in the society.