Google flagged US-targeted products because no sales-tax information was available for them. This check is largely retired: since July 2025 Google no longer asks US merchants for sales-tax settings or the tax attribute and estimates tax from the shopper's location instead. If you still see this issue, the account or feed is on an older configuration, or the product is really failing a related price or landing-page check.
Historically the cause was simple: tax was never configured at account level in Merchant Center and the feed carried no tax attribute for the states where you collect. Today it usually means a feed built from an old template, a platform integration that still submits retired tax data, or an issue date that predates Google's July 2025 change and has not been re-processed yet.