Can you change your shift?

I understand why that would be extremely weird but take it as an awesome compliment !

Time to have a short discussion about how this is very inappropriate in American culture. Let them know that you felt you should warn them before they lose their jobs for harassment by continuing this behavior with you or with other women (do so nicely). Tell them that they should ask American male acquaintances what they are doing wrong, too. Don't just shut up and tolerate it, they may be nice guys but they'll bug and pester another woman and she WILL turn their butts in. If they are new to the US, a factual statement and advice on who to ask is appropriate. Maybe one reminder if they do it again...and THEN go to HR. It takes time to acclimate to a new culture. Refusing to do so despite guidance, in a way that is a problem for others? That isn't appropriate. Here's hoping they just need facts and a pointer in the right direction!

So the real question everyone has is what gender is everybody here.

Remind them that they're not in Kenya anymore and we do things differently here.

Kenya believe it?!

Its not a good sign of a healthy workplace environment, be careful as well Op

I'm Kenyan, and I think they must be joking. Polygamy is legal, but I've never actually met anyone with more than one wife. It's not really part of the Kenyan culture in urban areas. Perhaps they hail from villages where that sort of thing is normal? Also, based on experience, a lot of Kenyan men will flirt with any lady they see. That's on the street, though... they are generally more professional in workplaces. Tell your co-workers that even though you're trying to brush their behaviour off as a joke, their comments/actions on this topic are making you uncomfortable and you'd like them to desist. I do think they are probably just messing around and will stop if they see they might have taken it too far... if they don't get the hint, though, you're within your rights to complain to HR.

Bullshit! I'm Kenyan and unless you work in the countryside, which I doubt, people don't have more than one wife or even propose marriage to people they barely know. Marriage proposals are more complicated and lengthy here. So..I call bullshit

Having been proposed to at work by customers... my default answers tend to be: "Sorry, I'm taken" "There's one thing I've learned in life, never date or marry your customers or coworkers." or in cases of polygamists (which I've encountered too): "I don't share well." "What? I'm not woman enough on my own?" "Sorry, polygamy's not my thing... nor is it legal in this country." "Honey? You AND your wife couldn't handle me. So how about you back off now, hmm?" If they don't back off soon, tell them that harassment is punishable by termination in this country, and consistently objectifying you is not appreciated. You don't mind a joke or two, but consistent fake marriage proposals are pushing it too far.