And you're speaking falsely when you say "God fully and completely judged America’s sins 2000 years ago." He did that for our sin, yours and mine, sins that we committed, not national sin. Plus that principle can only be applied where a person has come to grips with their sin nature and realize they are in a broken relationship that must be put right. That same principle does not apply to a nation.
There’s no such thing as “national sin”. There are only the sins of individuals and Jesus died for ALL the sins of the WHOLE world (John 1:29; 1 John 2:2).