They're just temporarily suspended until Aug 29. They don't want in-flight packages to arrive without duty paid and have to be returned. When they resume delivery, all new packages will have duty collected at the time of sending.
That said, it'll kill overseas direct to consumer businesses aimed at the US. No one wants to pay $80-200 per package for packages valued under $800.
Indiana is 7-2 Republican. Indiana has a very safe Democratic seat in Indianapolis. They can probably pick up one seat here.
Missouri is 6-2. The state is already gerrymandered as well, with very safe Kansas City and St. Louis seats. They can probably dilute Kansas City enough to pick up one seat as well.
Meanwhile, New York is 19-7 Democrat. Colorado is 4-4.
There are 15 states with complete Democratic state control, 11 of which have Republican seats.
Meanwhile, there are 23 Republican-controlled states, but only 12 of those have Democratic seats. In almost every case, those are just one seat because the rest of the state is already gerrymandered as much as possible. I haven't looked through them all, but those seats are probably packed already and therefore safe.
It's theoretically possible for them to pick up some seats from Georgia, Florida, and Ohio, but that would probably leave many of those Republican seats vulnerable with a thin margin.
If Democrats take control of the Minnesota assembly, you could see opportunities there.
Democrats are favored to take control of Virginia, which could have several more opportunities.
I'm saying this is a fight Republicans will likely regret starting.