Two other options would be:

A. End of the Molotov/Ribbentrop pact (any war with Russia is technically transcontinental)

B. British sinking of the Vichy fleet (happened in a lot of places right?)

Or paradigm adjustments to the two you suggested:

A. France/Britain declaring war in response to German invasion of Poland (committing their global empires to the conflict)

B. Japanese campaign in Malaysia and Indonesia adding that theatre to Japan's war and putting them at war with.... Ummm other empires.... I think British and dutch?