Tax-free in India, not in the US
In India these accounts are among the most tax-favoured things you can hold. An EPF balance is exempt under Section 10(12) after five years of service, a PPF is exempt under Section 10(11), and NPS is largely exempt on withdrawal. India taxes them little or nothing, in India.
The US does not follow suit. These are not US-qualified retirement plans, so the deferral India grants does not carry across. Instead, US tax tends to treat an EPF or PPF as a kind of foreign trust, and the consequence is that the income these accounts earn, the interest credited, and for an EPF the employer's contributions, can be taxable to you as a US person in the year it accrues, not deferred to withdrawal. So while your Indian statement shows tax-free growth, the US may be taxing that same growth every year.
Why there is no credit, and the treaty does not help
The part that makes this expensive is the absence of any offset. The foreign tax credit works by crediting foreign tax you actually paid. But India exempts these accounts, so you paid no Indian tax on the growth, which means there is no Indian tax to credit against the US charge. You bear the US tax on the accruals in full, with nothing to soften it.
The treaty does not rescue you either. It has a pension article, but the treaty's saving clause lets the US tax its own citizens and residents as if the treaty had not come into effect, and the private-pension article is not carved out of that clause. So a US person cannot use the treaty to make an Indian private pension or provident fund tax-free. Unlike some other countries' treaties with the US, the India-US treaty contains no provision that makes Indian retirement accounts tax-deferred for US purposes. A government-service pension is treated differently, but the ordinary EPF, PPF and NPS are not sheltered.
Reporting, and getting the right help
On top of the income tax, these accounts usually carry US reporting. Treated as foreign trusts, an EPF or PPF can require the foreign-trust forms, and the balances feed into the foreign-account reports, the FBAR and the Form 8938. Missing those carries heavy penalties of their own, separate from the tax.
The honest position is that how exactly to characterise and report an EPF or PPF for US tax is unsettled among specialists, so this is not a place for a clean do-it-yourself answer; it needs a US cross-border CPA who handles Indian accounts. What a practising CA on the India side does is give that specialist what they need: the year-by-year interest and contribution detail, the account balances and the Indian exemption position, so the US treatment can be applied correctly and the reporting completed. The single most valuable thing is simply knowing the exposure exists, so it is handled, not discovered later.