I'm no Trump supporter but I have some experience with the European anti-globalists and I can see some parallels.
Globalism is basically open borders, people can migrate freely and so can jobs. Of course, many people do not like this, working class people do not want their jobs shipped overseas and middle class people do not want their neighborhood filled with migrants living on section 8 housing or people with Burkas walking along the streets.
Really, there is nothing nice in walking around in Paris and seeing this:
These people are not going to take my job, I don't even need to work to keep a lower-middle class life to be fair. It's just disgusting. I'm not against all migration, it's great to have exchange students and Indian geniuses, and I guess some hard working people are needed to pick vegetables, but come on.
America doesn't have such a large problem, Latin American migrants are not the same as these boat people. It's just an example of globalism.
Having explained what is globalism and why it's bad, Trump basically said he was going to protect America from that. Of course he didn't because he was just trying to get elected. And that's it.
About the left, many of their policies are actually pretty good, universal healthcare, UBI, a safety net, whatever. They don't come alone though, they support high levels of migration (open borders is a strawman), including for humanitarian reasons, that is, migrants that are not needed or have a very minor effect on the economy.
Well, that's why secular middle class people are against the left and globalism. There are other groups, there are nutjobs (the UN wants to enslave us all), Christian anti-abortionists, and all kind of trash.
For the working class many were on the left but they feel left behind because the jobs moved to China and there is a lot more migrant competition and the left basically said that they should learn how to code or that it's all automation, a lie.
Sure, having better skills is great and robots can do things faster and better not to mention other technologies like strip mining that diminish the need for miners.
The problem is that not everyone can be a software engineer and there are a LOT of factory jobs in places with cheaper wages and lax environmental regulations. Corporations move there to save costs, that makes products cheaper and that's good for the whole but it's very bad for the individual workers.
By the way, in Europe there are left anti-globalist parties but these are not viable in the US due to the two party system.