The topic is sharing culture, where lots of very patriotic US things have their origins in other cultures. How so much of the US identity is a mish mash of other cultures. The US is even known as a cultural melting pot!

The hypocrisy is being ok with other cultures if you're familiar with them, but hating 'new' culture. The comic is criticizing xenophobia by pointing out the (somewhat) xenophilic history of US culture.

I mean, from what i can see by googling it, it does seem like it originaled in england and was brought over to america. The apple trees in america were crab apple trees and were useless for making apple pie. The apple trees you use were brought over and domesticated before baring fruit that could be used in the dish.

Also, when i say stolen, i am talking about using a dish that didn't originate in the USA to define the USA. But to mean that this pie is culturally american and patriotic. Except ironically it actually just proves how american culture is born of many many different cultures that came before it, and being proud to be american whilst simultaneously wanting anyone who isnt white to get out of the country is so idiotic and backwards.