True....to a degree. Our agriculture exports would soar. But alot of other things we produce are complex/advanced products, which depends on cheap parts/oil from....other countries.
As for the military, well, China will pick a good time to crash the dollar (when they've liquidated most of their dollar reserves). Then they'll be able to bring US to its knees without firing a single bullet. Why shouldn't they? it's their turn to be the empire.
China's is an command, export-based economy. Eviscerating its trading partners wouldn't be wise: high-interest rates and weak dollars in the US hurt the Chinese economy--like it or not, our fortunes are intertwined.
Empires are founded on more than just manufacturing capacity. Lacking a dynamic, principled base for its society, when the Chinese economy collapses it will not recover. The Chinese bubble will burst: http://www.foreignpolicy.com/articles/2009/07/23/the_china_b...
Upshot: don't finance your customers, or China 2009 == Lucent 1999
As for the military, well, China will pick a good time to crash the dollar (when they've liquidated most of their dollar reserves). Then they'll be able to bring US to its knees without firing a single bullet. Why shouldn't they? it's their turn to be the empire.