There are so many variables—the biggest of which is your personality and preferences—that it's difficult to answer this question. I haven't lived in Europe recently (though I did 30 years ago), but I have family members who are expats and I have friends there. Some of the people who are answering that the US is a better bet financially are clearly people who have top qualifications and jobs.

Setting aside the politics, your financial position and well-being in the US are dependent on 1) where you live and 2) your job. People with top qualifications in tech fields, medical research, or finance get salaries well over $200K, excellent health insurance, and lots of vacation time. They can easily afford housing in the places in the US with the highest quality of life. With your bachelors degree in international relations, I'm sorry to say that you probably won't be in this category. Instead, you will be scrambling for entry-level jobs that offer crappy benefits. You won't be able to afford to live in the parts of the US with progressive politics and high quality of life unless you want to share a room in an apartment in a lousy neighborhood. Even then, you'll struggle to get by.

I have what most people consider a good job, though I make less than $200K, and I'm not in a lucrative field. My health insurance premium is around $1,600 a month to cover myself and my spouse, of which my employer pays half. So $800 comes out of my pay each month. That's nearly $10K a year. This insurance has a $4000 deductible. So I spend nearly $14,000 a year on healthcare if I have medical expenses of $4000 or more before insurance pays a penny. Income taxes and Social Security take $30K+ out of my pay. Living in the US, you will need a car. That costs thousands a month when you consider all the expenses. Then there is the cost of housing. I live in one of the "better" parts of the country, and it is not cheap.

Arriving with a BA in international relations from a foreign university, you are frankly going to have to scramble to get a gig that is better than a barista at Starbucks. And if you succeed in getting what will probably be a soul-crushing desk job, you will face all of the costs I mentioned.

Unless you are in one of the glamorous European cities (London, Paris...), your housing costs will be dramatically less there. Your medical costs will be almost nonexistent. If you are in a medium-sized or even a small city, you really won't need a car.

Then there are the politics. Everyday life hasn't changed much in the United States yet (unless you are a brown-skinned immigrant), but many of us fear a crackdown is coming once the 2026 elections are past. The fear is that those elections will be rigged or otherwise manipulated to cement a Republican vice-grip on power that will then permit drastic cuts in social welfare programs without consequences. Medicaid is set for drastic cuts that take effect just after the election that will shut down rural hospitals and many nursing homes. The social consequences will be brutal, but with a stranglehold on power, Republicans will be able to suppress any unrest, perhaps suspend the Constitution. Until it is clear what is going to happen politically, I feel it would be very risky to move to the United States permanently.

I would advise you instead to pursue graduate studies in Europe that lead toward employment there. Do some research to find out what qualifications will offer you a working visa. Choose a program that involves practica with local companies. Make sure you focus on mastering the local language. You probably won't pull this off in an English-speaking country because there's so much competition, and the economies of the UK and Ireland are not looking great right now.