two continents of free wealth

that's basically it

if the western hemisphere didn't exist Europe wouldn't be able to colonize anything except maybe Siberia

Thinking too much about whether they could that they didn't think about whether they should

There's a good book I'd recommend which seeks to answer this exact question called Escape from Rome. Read the blurb to get a very basic picture.

https://press.princeton.edu/books/hardcover/9780691172187/escape-from-rome

I suggest Robert Marks The Origins of the Modern World. He's not a Marxist, but he takes a materialist stance on this exact question.

Basically since Europe didn't have an abundance of mineral resources like gold and silver, they couldn't compete with the other major cultures in Eurasia. China and India had much better manufactured goods, Indonesia had spices, and the Ottoman empire had Afghani silver and were the middleman if Europe wanted to trade with the east.

What European nations could do was fight, all they did was fight each other for the last 1000 years. So they turn their warfare on other nations via gunboat diplomacy. I could go on, but by the time of the industrial revolution England's coal deposits put them in a powerful position. English coal combined with slaves and looting of the continents propelled them until WW2. After that America took over as world hegemon.

Basically it's not a simple answer, there were many points where the dice could have rolled the other way. The materialist answer is not supposed to be predetermined, that's where Jared Diamond gets it wrong. A lot of things went right for European empires and they capitalized on it with their barbarity.

It's truly disappointing that nobody here seems to be aware of any of the Marxist literature on this subject. It's just a souped-up version of Guns Germs and Steel.