Are proper adverbs falling out of usage in current spoken American English?

Solution 1:

In that case "strong" makes sense to me because there's an implied "as":

You came across (as) very strong.

If you think about it, it could make sense to say

You came across very strongly as weak.

although it would be bizarre.

But to answer your question more generally, well, not really, except in extremely informal conversations. For example, "I'm gonna go to the store real quick," sounds normal to me (I'm American) but not "But to answer your question more general, well, not real, except in extreme informal conversations."

EDIT: I think these examples just happen to be informal colloquialisms. To me, going to the store "real quick" means something different than "really quickly". If someone said he was going to the store "real quick" I would take that to mean that he wasn't going to dally. On the other hand, if he said he was going "really quickly" I would picture him literally running there.