Actually, that issue is more nuanced than you thinks. Soviet Union overspent itself into oblivion. Military spending is transitory -- it does not last, so you should only spend as much as you need, and spend the rest on development. US is spending above global average (in percentage of GDP), so unless it can get benefit in excess of the cost, it's not a good strategy in long term. China is pending close to global average, so the effect is close to neutral pertaining to the global economic growth rate. Since no country see fit to invade China currently, it is more than likely enough. Whether it's excessive is another question, and Chinese government are more than competent in being the judge of that. Since military spending impose less burden comparatively to US, in the long run China would have advantage.