BTOT
iShares Total USD Fixed Income Market ETF
stock NYSE ETF

I'm only commenting here because I was linked here from a Google search, and I want to add clarification for anyone else that winds here.
BND (and AGG) already have about 7% international bonds. This is because they are not funds for "US Bonds", they are funds for "Bonds denominated in USD". "Yankee bonds" are non US bonds in USD, and included in these funds.
iShares has two more USD bond funds that include a larger swath of the USD bond market, IUSB and BTOT. This is where the emerging markets comes into play. The EM yankee bonds in IUSB and BTOT don't qualify for the index that BND and AGG follow.
Further confusing things, the index that BNDX follows mostly excludes EM. So BNDW, being a holding fund for BND and BNDX, also mostly excludes EM. You'll notice that IAGG, which follows a slightly different index, has a higher proportion of EM.
So if you want "all the bonds", BTOT + IAGG gives you the most coverage. But you have to question if that's worth it for you, I personally use BNDW for simplicity.

I'm only commenting here because I was linked here from a Google search, and I want to add clarification for anyone else that winds here.
BND (and AGG) already have about 7% international bonds. This is because they are not funds for "US Bonds", they are funds for "Bonds denominated in USD". "Yankee bonds" are non US bonds in USD, and included in these funds.
iShares has two more USD bond funds that include a larger swath of the USD bond market, IUSB and BTOT. This is where the emerging markets comes into play. The EM yankee bonds in IUSB and BTOT don't qualify for the index that BND and AGG follow.
Further confusing things, the index that BNDX follows mostly excludes EM. So BNDW, being a holding fund for BND and BNDX, also mostly excludes EM. You'll notice that IAGG, which follows a slightly different index, has a higher proportion of EM.
So if you want "all the bonds", BTOT + IAGG gives you the most coverage. But you have to question if that's worth it for you, I personally use BNDW for simplicity.