Parents said they expected backlash but hoped people would have behaved a "little more respectful" towards their son.
"If you liked the president's border wall, wait until you see his space wall," arms control expert Joseph Cirincione said.
"Great job by Michael Anton on @foxandfriends," Trump tweeted. "A true National Security expert!"
The University of Iowa student was allegedly killed by a man who had entered the U.S. illegally from Mexico.
The president made his feelings clear in a series of tweets.
Kushner's Mexico trip indicates he will still play an integral foreign-policy role, despite losing access to classified information.
Presidential candidate Ricardo Anaya said Mexico will refuse to pay for constructing the border wall, as Trump once insisted would be the case.
The administration has not provided any "definitive real estate costs or requirements" about its border wall plans, a report found.
"If this fence is inevitable, it might as well be built well, and by us," one firm said.
The report from Democratic staffers of the Senate Homeland Security and Governmental Affairs Committee said vital programs could see their budgets slashed.
The bill includes measures such as five-year prison sentences for those re-entering the U.S. illegally after having been deported and the forced use of electronic ankle monitors.