We do need better immigration laws and enforcement of existing labor laws, but a wall will not solve it.
50% of illegal aliens enter through legal points, then overstay visas. A wall will simply make this proportion grow.
A wall is defeated many ways, with ladders, small planes, tunnels, boats at sea, hot air balloons, not to forget, it can be damaged in multiple ways with bombs, bulldozers, and other heavy armaments that drug cartels will make a point of honor in using.
True enforcement of labor laws, including, throwing in jail (with long mandatory sentences and disabling fines) the American employers who offer jobs to the illegals, would do a lot more to curb illegal immigration than walls.
This should be coupled with reform in the way someone qualifies for immigration (to make it merit-based rather than family reunion-based), and enhancement of non-immigrant work permits.
So, no, no emergency.
The appearance of an emergency was created by the Trump administration (the humanitarian part, which is a refugee issue, not an illegal immigration issue). Drugs and illegals enter mostly by legal points.
If a wall is built, it will do nothing to stop the influx of asylum seekers. They just need to present to a legal entry point and petition for refugee status. And it will do little to curb the problem of illegal immigration.
If we keep offering jobs to illegals, they will find a way to come, wall or not. If we stop offering jobs, they won't come even without a wall, and the ones already here will leave.
I'd favor focusing all the resources into enforcement of labor laws. The billions Trump wants for the wall would be more efficiently spent on hiring Labor Department auditors.
If we did all that and money were still available for more, then, sure, some physical barriers might help a little. But focusing on a wall without fixing anything else is an obvious waste of tax-payers money.
Unless Mexico pays for it... that was the original plan, wasn't it, Donald? So why are you now asking us to pay for it?