The Aspirin and Heroin trademark revocations were punitive and due to the war, not due to lack of proper defense.
That’s why you will see non-Bayer acetylsalicylic acid literally marketed as “Aspirin” but even though the Kleenex trademark is considerably weakened, you still don’t see competitors openly labeling their products with the name.
Xerox was eventually successful (at least in US), but there are cases like Bayer's Aspirin (surprise!) that were genericized.