If you feel you must derive the rule that God "always" supports illegal aliens, then go for it.
I see alternatives.
However, in that particular instance God did support them.
"Since God did X in situation Y, then God will always do X for any situation" does not seem to be logical to me.
That does not change, though, that God did do X in situation Y.
Then your posting of the story of Joshua was meaningless. There is either a principle there that you're applying to the situation or there isn't. Now you are claiming there isn't.