June 18 (Reuters) - Meta Platforms has lobbied the U.S. Congress for legal immunity from child-harm claims tied to social media products such as Instagram, as it faces thousands of lawsuits from young users and their families, according to a source familiar with the matter and proposed legislative language reviewed by Reuters.

If adopted by lawmakers and passed into law as part of the Kids Online Safety Act (KOSA) under consideration in the U.S. Senate, such a provision could undermine thousands of lawsuits against Meta and other online platforms over harms to children. Meta and Google's YouTube face a combined $6 million in damages after they lost the first case at trial early this year.

While legislators have given no indication of adopting the language, the lobbying effort shows the kind of legal protections Meta is seeking amid the biggest attempt to regulate online platforms in the U.S. since the 1990s.

Meta declined to comment on Thursday. The company has previously called for federal standards that would require app stores to verify age and replace state laws on children's online safety.

The proposed language reviewed by Reuters would make online companies "immune from suit or liability under state law" for claims relating to children's online safety. The provision appears alongside language that would preempt state laws on children's online safety and privacy.

Meta has proposed the language in exchange for dropping its opposition to KOSA, the source said. The bill, sponsored by U.S. Senators Marsha Blackburn, a Republican, and Richard Blumenthal, a Democrat, would require social media companies to take reasonable steps to prevent certain harms to minors, such as compulsive use of their platforms.

Under KOSA, companies would be required to exercise care in deploying specific features including infinite scrolling, activity notifications and appearance-altering photo filters.