Americans should be careful about using the cryptocurrency Tether because of its use by terrorists and drug cartels, according to a new multimillion-dollar campaign by a consumer group. Consumers’ Research, an independent education organization for consumers, launched a multi-pronged media campaign on Tuesday warning that Americans might be opening themselves up to financial risk by using Tether. Tether is one of the world’s most commonly traded cryptocurrencies and is linked one-to-one to...