Most states in the US could use a photo of a teenager in a bikini as enough 'evidence' to bring charges of Possession of Pornography involving a Juvenile, depending on what the actual photo depicts. Whether the contents of the image could be found to substantiate a conviction for the charge would be a trial/appeals issue. Nudity is not required for an image to be considered CSAM in most US states (or at the federal level), there are also Federal precedents that make cartoon depictions of under-aged characters count as CSAM.