I understand this is the common usage, but that is no reason not to object.
One can't see they are Asians.
One reason why unknown numbers of Libyans, Bosniaks, Chechens, Pakistanis, etc.--- and that comprises Africans, Europeans, and Asians --- are slipping over the U.S. southwest border and disappearing into the U.S., is that they are Muslims AND that they can't be visually distinguished from Mexicans, Salvadorans, Nicaraguans and Guatemalans. Put on a jacket with Lindo Michoacan embroidered across the back and have him say his name is Flaco, and as Joe Biden would say, "Bienvenidos, hermanos, we're all Amerians here."
These particular people I'm talking about are not Asians and not distinguishable from other immigrants by their appearance. They're coming because they're Muslims and it's a safe bet they want to wreak havoc.
It would be seven kinds of stupid to call them Asians. The relevant detail, what gives them an operative characteristic in common, is that they are Muslims.