Yes, either phrase is usually understood by American readers. However, "I could care less" has a literal meaning opposite from its idiomatic meaning and is lik

Yes, either phrase is usually understood by American readers. However, "I could care less" has a literal meaning opposite from its idiomatic meaning and is likely more troublesome for non-native or non-American readers. Also, when many people read "I could care less", they assume the writer has a deficiency in their education and/or attention to detail. Seldom is it advantageous to write "I could care less" instead of "I couldn't care less".