What a Japanese victory at Attu would provoke

What if Japan had successfully relieved Attu and defeated the American invasion force?

The United States would probably return with a force two or three times as large.

The scenario assumes that a Japanese relief fleet reaches Attu and sinks the American invasion force in 1943. The predicted American response is to rebuild what was lost. The replacement would probably be much larger, described as being rebuilt in double or triplicate. This is a brief counterfactual judgement without a detailed account of how the renewed campaign would unfold.