The US default withholding on dividends paid to a non-resident alien is 30%. If you file a W-8BEN claiming India treaty benefits, the rate drops to 25% for most retail investors. Through an IFSC structure that elects the LLP/partnership lookthrough, certain investors achieve 15%.
Interest on most US government bonds is portfolio interest and exempt from withholding entirely. Capital gains on US equity are taxed in India, not the US — there is no US capital gains withholding for non-resident aliens on listed securities.