Because communism is a specific ideology in which private property and money are abolished, and people work only for their own pleasure. This is a theoretical stage developed by marxist theories that has never been reached.
An American politician calling for more government intervention can fall under a myriad of political ideologies: from social liberalism, to social democracy, to even democratic socialism. Thus, it is not accurate to label someone like that as "communist".
There were several ways in which the US government increased Mexican immigration, but the best option is "congress passed laws saying that all Latinos fleeing dictators are welcome"
