It depends on their relationship with the social media companies. There's a good chance companies like Meta have already given the authorities a lot of data on their users. US law enforcement might already know about some of your accounts based on your identity, and then claiming you have none might not work well.

If you can't prove Social Media history, you don't get in, they arrest you, and deport you without due process to a life sentence in an El Salvador torture prison where you'll never be heard from again.

Just tell your employer you're not going.

My employer issues us with a wiped laptop that we can restore from cloud storage over our VPN once we're in-country. Before we return, we back it up and scrub it again. When I go to the US, I always bring a low-functioning burner phone as well.

How will they prove that I have any social media history?

Hard to say what the US government knows, or admits to knowing, about your social media usage. I almost completely stopped using social media a few years ago, except for Lemmy, and overwrote all my posts with lorem ipsum, as well as never having accessed it before that without using a VPN and doing some other obfuscation, so it'd take some effort to associate me with anything but some boring Facebook and LinkedIn updates I maintain so that certain people can still get in touch with me.

Have you heard about 'age verification' to 'protect the children'? You too will be age verified. They will know all your accounts. That's the whole point of age verification. It is to eliminate anonymity.

Just tell them you were born yesterday

If it's a US based company, the NSA has all of your web traffic to the site.

Facial recognition software.

Did you not see the group of tech billionaires behind Trump when he was sworn in?

You already need to provide all this for a work visa.