Of course. One can definitely cherry-pick a Massachusetts-sized sample from a US-sized country, but it's rather hard to cherry-pick a Massachusetts-sized sample from a Massachusetts-sized country.
Because even compared to Massachusetts, which is anything but homogeneous, the US at large does miserably.
But actually ... fairly representative of most other states. If anything... Massachusetts should have MORE education problems than places like Nebraska, Washington and Missouri.
If you look at the section titled "Breakdown by State", the numbers for Massachusetts and New Jersey are far and away larger than the numbers for ... say ... Nebraska and Washington State. Yet Massachusetts and New Jersey are top 5 performers on international tests.