Open borders are a joke and only serve the business owners. Immigrants are almost always cheaper to exploit and if these same immigrants don't assimilate to the culture of the land they are migrating to, they weaken the overall stickiness of the society.
When a country has most of it's citizens all looking the same, speaking the same, and worshiping the same, adding in a culture that doesn't want to change, doesn't speak your language and doesn't look or dress like you do just adds pressure to social cohesion.
I wish those immigrants never founded my employer and about 1/2 of my entire industry!...not to mention bolstered us and made us superior to all the companies based in countries that were hostile towards immigrants. Not sure if you're American, but for all of our problems, we're one of the most accepting of immigrants in history. That's why we prevailed and our rivals fell short, especially the Soviet Union, post-war Japan, Korea, and China...and in the future it will be Israel and maybe some parts of Northern Europe. We produce a lot of talent locally and what we don't produce, we happily import.
Also, fuck off with the open borders bullshit. No one wants completely unregulated immigration. The far left in the USA and presumably everywhere else just wants lots of opportunities to move here...not let ANYONE without any sort of security checks whatsoever.
However, what has made the USA home of many of the greatest businesses and especially startups is that we not only welcome talented immigrants with open arms (at least we definitely did pre-Trump 47), we gave them loans and investors mentored them to succeed. This applies to Google, co-founded by an immigrant, as well as American-founded businesses like Facebook who filled their ranks with the best they could hire from around the globe.
Here's your choices...immigration as it is today with mild reforms, like better security checks or more legal pathways to citizenship...or...
We crack down on immigrants to the extent you and the Republican party says they want to and experience:
Food shortages, higher prices, the entire tech industry and every American multi-national literally decimated and relocating overseas to places that aren't hostile to immigrants. No good jobs, horrible inflation, bankrupt gov with no power to step in, Social Security running out of funds VERY abruptly, our entire economy and way of life wrecked...and like most failed states, like Russia, the very people with the talent needed to fix and rebuild will go somewhere else: Canada, Australia, maybe someplace crazy (except apparently Switzerland now?) and boost their economy....ensuring all American companies get killed on the international market.
All you MAGA folks...America is pretty great, especially compared to our rivals...and immigration is the main reason. We produce great talent and innovation...but more importantly, we attract immigrants who are talented and ambitious and ensure they start their companies HERE!...and not in their home countries. Most foreign economists bitch about this endlessly, the great American Brain Drain...where so many companies that would have been started in Europe, Asia, or India get started in the USA and we poach their top talent. So yeah, tolerate some people of different races and with funny accents and enjoy national prosperity?....or let those immigrants create jobs in their homeland at our national expense and see our economy much much worse....your pick!