Meta has already got fined for more than a billion at one point for breaking the GDPR, which has smaller fines than the DMA. The US did not really do anything. The US will not go to war with its biggest ally over Apple, hell, it doesn’t stop militarily supporting key regional allies over genocide.

Also, fines are not based on market capitalization, but on global revenue. How this would bankrupt Apple is not that the EU would bite off a trillion, but that they would grab a few bil from the revenue, and that would put Apple in the red, triggering selloffs and Apple’s valuation evaporating.