No, unfortunately not, says Dhirendra Kumar
Is there any Indian mutual fund route to investing in US Treasury bonds or any developed economy's government bonds?
No, unfortunately not and I also think it may be a novelty. But why should one invest in such bonds? Maybe, the impact of the domestic currency depreciation on the foreign currency-denominated bond will bring some appreciation for you but otherwise, foreigners find Indian bonds to be yielding a little bit more. So, there isn't any investment case for these bonds.
Hence, why should an Indian invest abroad in treasuries which will not yield anything or something insignificant? And perhaps because of this reason, there is no Indian vehicle that enables you to buy treasuries abroad.