The biggest challenge is for guys who cannot live there for awhile. They turn to the internet both for speed and convenience. Which can work if a fellow is careful and as things progress have pointman check them out. There will always be surprises whether your in person or online after people are living together. My last gf in the US was a completely different person after the 2nd year and had to go. Or maybe I just didn't see it and it was already there.
When a guy has 2 weeks to a couple months to meet a girl and make a decision things will move fast. So if he is 30-40 range he is taking a risk meeting and marrying quickly. Yet what is the available pool of gals in that age range back home? Divorced, bitter, 2-3 kids, and looking for sugar daddy no less than the 20 year old there. At least worst case he's getting a young pretty gold digger, and if he's careful he's just getting young, pretty, gold.