This is the only episode of the series to be animated entirely in America. This is likely due to two factors: Not much new animation was required for a clip show, and much of the new animation created was very limited in movement and thus, easy to produce domestically. See more
Yes, the Simpsons have come a long way since an old drunk made humans out of his rabbit characters to pay off his gambling debts. Who knows what adventures they'll have between now and the time the show becomes unprofitable?