It's pretty hard to take any effective
action with the feds throwing all they
can muster at you to prevent your
interfering with their plans for filling
the country with illegal invaders.
The citizenry could and would certainly
stop any illegal incursions at the
southern border, but the feds would
do everything within their power to
crush any action they saw as a threat
to their authority, and using deadly
force against the citizenry isn't a
far fetched possibility. Using gubmint
agencies and bureaucracies to
financially ruin citizens isn't far fetched
either.