Most illegal aliens enter the U.S by air. Do you agree that instead of a wall, we need a roof?

  The first sentence is either completely in jest, logically inaccurate or wholly unsubstantiated without further evidence. As such, the roof idea is held in abatement until further information can be supplied by its author. 
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Please do not give Trump any ideas...

i highly doubt 'illegal aliens' can enter USA illegaly by planes.... they all need visas and ID and all that 

Not such a far-fetched theory, I guess.  Oh look, here they come now! :P

How about a giant dome? Maybe even a huge sphere so that they can't try to dig their way in?

I have to agree with Randy about the first statement. References pleeze.

I think we need a new electorate. The ones we have forget that they are all descended from illegal immigrants! One American out of eight lives in California, and that was a spoil of war. They only made it a state because the army didn't want to be bothered with running it. Texas was a similar deal. There were no injun wars on the east coast because most of the injuns were wiped out by an epidemic just before the puritans arrived. 

At one time the American attitude toward immigrants was so good that France gave us the Statue Of Liberty specifically to celebrate it. WTF happened since then?

Not quite, it's about 40% by air and 15% by sea. Ergo, a wall will do nothing to deter more than half of all illegals.