It would be a Social Media position. Do I just file a tax report as a freelancer then? Do I need a business license for it? The company has no ties to the US at all. What do you recommend what's the best thing to do?
Fellow US-German here with freelance clients in Germany. First, your immigration status is important. If you're not allowed to work in the US, it's my (non-lawyer) understanding that you can't engage in work, not even as freelancer.
If you're allowed to work, then, as a freelancer, you'll be subject to local (e.g. city, county) or state rules. In most places you may need to get a business license, which usually is not very expensive (where I live, it's about $150/yr). Some municipalities don't require a business license if you're not actually doing business in the municipality you live.
Once all that is sorted out, you can just do work for your German client, invoice them in USD, receive international payment (Paypal, bank wire, crypto), and then report this as business income on your tax return. That's it.
This is smiler to when I was in the UK as a US citizen. They had told me that if I am a US citizen doing work remotely on systems in the US then I would only be obligated to US laws and regulations for the work I was preforming. Even though my physical presents was in the UK. Though legal definitions in this area are vague, as long as I am not doing anything that would other wise be illegal in the US or the UK and I am not overstaying my 6 month visitor's visa / attempting to use it to take up residency in the UK, it was alright for me to work remotely.
It will depend on your jurisdiction - state/county/town(?) - whether you're required to register your business. You probably will be. I (US Citizen, working in the US) had to register my freelance business in Massachusetts and in New Hampshire (at the times I lived in each one) and pay a few dollars - a tax - to do so. I don't remember the registration price in Massachusetts, but in NH it was $50, good for 5 years.
You have the additional wrinkle of being a non-citizen. I have no idea how or whether that might change anything, even assuming you have the right to work in the United States.