Doubtful. I can think of no practical way for American LE forces to effectively search every room of every home and find every firearm. There are just too many homes, too many guns, and not enough LEOs (even with the ARNG). Add in some opposition, and the whole thing becomes a nightmare that no LEO will be eager to pursue, especially day after day for months.
But if it does happen, and it is "done quickly," then that's on us. Whenever confiscation happens, if it does, then it's incumbent on gun owners to make the process as deadly and lengthy as possible for the JBTs.