I wouldn't be surprised. Daniel Dines started UiPath in Romania but for it to become truly global, he had to move to NY and even incorporate the company there.
I don't want to insult Romania (and I actually am looking forward to an opportunity to visit it, there apparently are many spectacular places, nice people and delicious cuisine), but AFAIK it's rather far from the best places in the EU from the economic/social points of view, no surprise many people prefer to emigrate on a good opportunity. I would be more curious if founders still move to the US from Spain, Germany, Switzerland, Netherlands, Ireland etc.
UIPath has a huge development office in Bucharest, most of the company is there.
Don't kid yourself, he went to NY for the money :-))
If they want to do business in the US, they often do; the US market is very protective and isolationist like that, for some reason. An EU company doing business with an US based company is a lot easier.