All major (and some minor) world powers are invested in this war in some way. China, Iran, India, the US, Russia of course, Europe. By population that's a lot. By power or influence that's also a lot. I think the main difference is the overt-ness. War has changed a lot since WWII, was have a lot "safer" and longer distance tools, including financing. Financing is way different now, it's instant for starters.