Nonsense. Massachusetts isn't gerrymandered at all. There isn't a map that could be drawn that would create a single Republican district anywhere in the state.
See for yourself. Massachusetts 9th Congressional District is the only one in the state with more than zero precincts going to Republicans, and it still went +13 Democrat.
Popular vote percentage versus percentage of districts won is a poor metric for identifying gerrymandering. In most states, over/under representation in the house tends to be a function of urbanization rather than gerrymandering. Rural regions lean overwhelmingly Republican, and urban regions lean overwhelmingly Democrat. Naturally, this results in regions of concentrated support for each party. Nonetheless, there are still members of each party in both regions in meaningful numbers whose votes are overwhelmed by the dominant party of their region. The result is that more urbanized states (California, New York) tend to overrepresent Democrats and less urbanized states (Missouri, North Carolina, Ohio) tend to overrepresent Republicans.
Illinois is the preeminent example of a partisan gerrymander. Still, eliminating this gerrymander would net Republicans no more than 3 or 4 seats, which is not enough to balance the popular vote versus districts won. California, if they eliminate their non-partisan redistricting commission, could create a map with nearly all districts leaning Democrat by partitioning the populations of Los Angeles, San Francisco, and San Diego with rural areas, eliminating up to 9 Republican seats. New York, with its population so concentrated in NYC would have a more difficult time creating such a partisan gerrymander, but they could probably eliminate the 3 Republican districts on Long Island and Staten Island without much difficulty.
Texas already has some pretty egregious gerrymandering.Republicans should be wary. Parceling out Democrat populations into Republican districts necessarily makes those Republican districts more competitive. If Republicans have a poor showing at the midterms, then such a gerrymander could seriously backfire. Conversely, the same applies for California, Illinois, and New York Democrats if they have a poor showing.