The folks who decided that mailing bricks to Congress is a good way to lobby against immigration picked an ironic symbol. Who exactly do they think builds America's brick walls? Have they been to a construction site lately?
Real invaders don't build buildings. They blow them up.
UPDATE: This Fortune article estimates that "up to 40 percent of new-home construction in the U.S. is being done wholly or partly by undocumented immigrants," possibly as much as 80 percent in Texas. Referring to Latino immigrants, legal or illegal, one contractor says, "If for any reason we lose that work force, you're going to see the time required to build a house double or triple and the cost of new homes increase 30 to 40 percent." And don't even think about remodeling.