I don’t think any of his books were political.
If there was any political angle in a Seuss book, it was so low key and discreet as to be easily ignored. I’m convinced Seuss didn’t like socialism, though. Even the NYT (albeit from decades ago) called the animals who took up residence in Thidwick’s antlers, ‘spongers,’ (who got what they deserved).
Then there’s my all time favorite, I had Trouble in Getting to Solla Sollew. On the one hand you’ve got the side that promises unicorns and skittles but fails to deliver. Otoh is an individual who gives up on overreaching promises and who decides to deal with his problems with his own big stick. No way is that liberal.