Most likely to Japan. Then again, there's also the Reichskolonialbund where Germany could purchase the Philippines again if Japan controls it. Perhaps with the signing of the Tripartite Pact or an event that happens a lot earlier would have resulted in Japan's sale of the Philippines to Germany under the Nazis. I would have shuddered at the mere thought of the Nazis goosestepping in Manila.
Crap, you just gave me nightmares.
You know what would be better for Prussia's economy, Uniting Germany
Or before 1800, consolidating its position as a great power.