Canada
20 questions, 30 minutes, oral interview. No written test. Officer asks questions, you answer verbally.
USA
10 civics questions from pool of 100. 6 needed to pass. Plus English assessment (speaking/reading/writing).
Australia
20 multiple-choice questions, 45 minutes. 75% required (15/20). Multiple-choice format easier than essay.
UK
75 multiple-choice questions, 45 minutes. 60% required (46/75). Longest test, most content.
Hardest?
UK (most content) then Australia, Canada, USA easiest (fewest questions required).