144 years ago some 600,000 Americans died to prove the US of A is an exclusive club you can never leave. Do not fool yourself, the Civil War was not about slavery -- no matter what your teachers told you.
With the exception of a few States in New England the majority of volunteers for the North were fighting to preserve the Union. There are thousands of diaries, memoirs and newspaper accounts from the era that back up this assertion. If the States outside of New England thought for a minute Lincoln would abolish slavery, there would have been few who rallied to the call to arms after the bombing of Fort Sumter.
In 1865 most citizens were farmers or craftsmen. The biggest factor in the Union victory was the industrial might of the nation lay in the North. The South was crippled by a blockade. The fall of Vicksburg was the beginning of the end. You should have learned this in 8th grade US History, but do a little research.
Today the economy is splintered in a similar way. No single region has a monopoly on resources and industrial capabilities. We are in a national and global economy. Let us look a simple commodity and see how a Republic of Texas at war with the Union would fare. Since the new Republic could no longer use the dollar as currency it will have to back its securities with other commodities. Luckily Texas has some oil. To pump that oil you need pumps, drilling machinery gears and bearings. Let us see there are ZERO bearing factories in Texas. A simple blockade of Galveston stops imports from China and Europe. Besides, what nation is willing to risk a trade embargo with the Union? No bearings, no oil, no trade. Can Texas produce enough food to feed itself?Is the State in a position to maintain the infrastructure? Texas has a GDP similar to Canada, but can it maintain that level of activity without the other 49 states contribution in food, electricity, water, raw materials, components?
I, for one, am not so sure the armed forces of the US will be so quick to ignore their oath to support the Constitution and the commanders appointed over them. They may not respect Obama, but you are gambling a lot on the idea they will not support the Commander in Chief. The idea of a military Coup d'Etat is a repugnant idea to most veterans I know. After all they followed the idiotic rules of warfare in Vietnam when they knew it would cost more US lives.
Talk of secession at this point is premature. If Americans feel strong enough the 9th and 10th Amendments should be enforced it will be done at the ballot box in 2010.