Unlike Rule Britania, our navy, army, airforce and offensive nuclear capability is still great enough that we can back up our empireish trash talking. The F-22 can outfly and outfight any and all comers, and it itself is not composed of our latest technology at this time. Our submarine fleet is larger, faster, and quieter than any in the world, especially China's akula clones. Our Nimitz class aircraft carriers allow us to project power anywhere, and the new Ford class carriers will further multiply that advantage. The M1-A1 is 20 year old technology, yet still the best main battle tank in the world by far.
Brasil lacks the hardware to really affect anything militarily.
India is trying to aquire it from russia, and they have the money to make that happen at the moment, looking at their recent purchases. Navalized Mig 29's (arguably the best aircraft the Soviets ever designed) The Admiral Ghorshkov (sp) aircraft carrier they are purchasing, which is about the closest thing you can get to a Nimitz class carrier, the Akula II attack submarines they are purchasing if the freon fire suppression systems don't kill everyone, but they really don't have the cultureal drive for empire, especially with pakistan to deal with as an external agressor.
China, China still is behind us in several key areas. They currently don't do aircraft carriers well and their domestic figther aircraft designs are years behind everyone right now. Submarines they definitly have an interest in, but even there they are significantly behind because Sovier russia never really shared much in the way of design material with them because they too didn't trust china. Their tank designs are mostly Soviet era hardware, which the M1-A1 is an effective counter for. What china does well though, is infantry, and missiles. Their training program for field soldiers is closer to the Russian Spetznas program than anythign we have, and they have more people to throw at military training than we can field. Their army is several orders of magnitde larger than our own, and just as well trained and equipped.
Missiles, we did have an edge over china, but since we basically gave them our entire guideance and targetting package 10 years ago, there is no real difference in tactical capability except our stealth systems are better, and they don't really have a "missile shield" program. They have very effective ICBMs and missles, native Uranium deposits, and the hardware to churn out nukes at an alarming rate though. They have not tested a fusion weapon to my knowledge at this time, but that could be either because they never recieved the technical package from the Soviets and chose not to persue it, or they have a design they just have chosen not to show.
China's economy tanked even more than ours did just recently too by the way.