I know many in the Military and in our local Police/Sheriff offices that take their oaths seriously and have commented that they will not betray their fellow Americans. That being said, I believe the Constitutional fight being waged is one of attrition being fought on our children. When the current generation is gone the one that takes it's place will have been raised without a sense of correct historical awareness and patriotic duty to this Country, accustom to a cashless society and dependent on the government. We are all but there now.
The only way I see for an immediate confrontation would be via a total economic collapse, ending in martial law.
Similar problems are facing the EU as the biggest hurdle is National Sovereignty amongst it's members. The EU has no direct authority over it's members, other than sanction/withholding aid. The EU can't make any single country do anything as all members retain their own National Sovereignty and all measures have to be voter approved. This was seen as the biggest problem in the EU's inception .
Imho, the only scenario to break these would be a total worldwide fiat collapse where a new global fiat union, replacing the greenback would be instituted. Admittance into this would be a relinquishment of some or all national sovereignty with the possibility of being policed by a some sort of UN type authority. All international trade would be suspended to holdout countries. The failures of the prior EU regarding members independence would be cited.
Unfortunately, given the choices of financial meltdown or an olive branch by some NWO I think the vast majority would sell themselves to keep a diminished but somewhat normal standard of living. I can see this scenario ending in an armed confrontation, with few holdout citizens against a NWO military.