Males 16-60 aren't allowed to leave Ukraine. They also have prevented "transexuals" from leaving. Unlike the "refugees" from Mexico and Central America, the Ukrainians trying to enter the US are overwhelmingly women and children.
Many of these woman and children will not be returning to Ukraine - nor their husbands in some cases. Once they get a taste of a world outside of Ukraine the attraction will be to great to resist. It’s one way to become European for sure.
As for living here in the US - they’ll never return.