[1/3] A Taiwan flag can be seen at Liberty Square in Taipei, Taiwan, July 28, 2022. REUTERS/Ann Wang/File Photo SYDNEY, June 20 (Reuters) - Australians would support responding to a Chinese attack on Taiwan with economic sanctions, arms supplies or using the navy to prevent a blockade, but don't support sending troops, an opinion poll to be released Wednesday finds. Canberra says it is opposed to any unilateral attempt to change the status quo in Taiwan, while the United States has long stuck to a policy of "strategic ambiguity" over whether it would respond militarily to an attack on the...