Yes leftism is often associated with communism. In the US the democratic party is considered left/liberal/progressive/socialist, and more recently has started to embrace some of the ideals of communism.
Republican is considered right-wing/conservative/capitalists and are often called fascists, but they really don't have any fascist beliefs.

The problem with communism is it's track record of killing millions of people wherever it's put into effect, and the fact that it always maintains an elite/wealthy class despite being created in opposition to that.
But also, the way it perpetuates itself is to sow unrest. Usually it's about convincing various racial, ethnic, or religious identities that they are being oppressed. Eventually convincing all of the lower or even middle class that they are being oppressed by the wealthy and the government. Communism has some good ideals, but it also has almost a religious sense of righteousness where they know better than everyone else.

On the other hand, capitalism eventually leads to problems as well. In the USA major corporations achieve a top position, and then start lobbying the government for higher regulations that prevent competition from forming. Also social-media sites push ideologies and suppress other ones. They also censor on behalf of the government as a way of getting around constitutional laws that prevent the govt from doing so.
This is why I think nationalism has a place. Because it can curtail capitalism's tendency of doing harm to a country simply in the interest of higher profit margins.

China somehow is communist, nationalist, and capitalist lol. They definitely have expansionist aspirations too. Is China a major player in Indonesia if the govt is very anti-communism?