Why would Japan involve it self against the U.S and the U.K? ...
The answer to that lies in a relatively obscure proposal to enact a draconian set of embargos against Japan. Those were discussed by senior US and British leaders in 1941 in response to Japans occupation of French Indo China. Why that embargo plan was not enacted is a complex bit of history I'll not address here. Suffice to say the proposals if carried out would have wreck Japans economy in months & bankrupted the nation inside a year.
1. Freezing/impounding all Japanese assets in US and British banks.
2. Sanctions against any nuetral nation that assists Japan in circumventing the banking freeze.
3. Preventing all US/British controled cargo ships from servicing Japan
These three items alone would cripple Japans economy. Approx 40% of the cargo clearing Japans ports was carried in ships controled by the US and Britain. That alone stalls Japans economy. Also Japans government and industry were heavily dependant on loans obtained in the London and New York banks. Freezing Japans assets in those would wreck its delicately balanced cash flow.
4. Prohibit the sale of a long list of critical raw materials & finished goods to Japan. In 1941 the US provided over 70% of Japans petroleum.
5. Prohibit the purchase of a equally long list of items from Japan.
These two items are almost redundant since the imposition of items 1,2,3 mean Japan cant purchase or import all it needs anyway.
Had these embargos been imposed Japan would have three choices. 1. See its economy wrecked in 6-10 months. 2. Capitulate to the demands of the US/Britain so the embargos would be lifted. 3. attack the US and Britain in a effort to force the lifting of the embargos & gain other concessions. I'll not say for certain Japans leaders would have choosen war, but option 1 was simply insane & option 2 would turn Japan into a client state of the US or perhaps Britain & see its effort at empire & idependance destroyed.