For a little clarification,: The Department of Energy says it has about 59 days of import protection in the SPR. This, combined with private sector inventory protection, is estimated to equal 115 days of imports. However, the maximum total withdrawal capability from the SPR is only 4.4 million barrels (700,000 m3) per day, making it a 160 + day supply [Not counting the private sector]. Though again, it is not counting the natural oil reserves nor current native active sources, and merely what we have in storage on-demand.
All in all, not bad, not great but not bad and certainly better then most. However, in today's economy, denying any major world power, especially the oil-guzzling USA, any and all Oil Imports would create a global shockwave of economic insecurity via direct impact and secondary trade embargoes which would pretty much screw up other world powers. Everyone's imports and exports are too closely tied anymore to make major powers warring with each other a practical option, which is part of the reason why major powers nowadays merely yell at each other and slap wrists.