(IMNSHO, Kentucky should have been in the vanguard of legalizing and growing THC and selling it to other states. That it hasn't and that it isn't, is a huge economic blunder on the part of the state, and I'm feeling it is high time Kentuckians shut up about coal, but what do I know.)
It was considered so fundamental during the drafting process that there wasn’t a need to enumerate “freedom of movement” specifically.
Interesting question. Not explicitly, but the Federal Government reserves the right to regulate "interstate commerce," which is a power granted specifically to prevent hard state borders, among other things.
States/municipalities do have mechanisms to screw with people from other states via tax and transportation manipulation. But, for the most part, I've never heard of any animosity towards local residents from other states, and I live and work in a city whose metro-area spans three states. Immigrants from other regions are different beast though.
Based on the data I can gather from a brief search, it looks like in 2017, 58% of Americans live in the state of their birth [1]. Because many people move states and then move back (for college or a temporary job or something) then it's reasonable to think that perhaps 50% of Americans move states at least once in their lives.
In 2016, 93% of EU residents were living in the nation if their birth; 4% were from outside the EU and 3% from another EU member nation [2]. (In the US, 14.4% of the population are immigrants, and this is ~20% of the total global immigrant population [3].)
Furthermore (and in the absence of any supporting data), I think that the assimilation process is for the most part easier for Americans moving between states, especially those who are at least second generation American. While there are definitely strong cultural differences between US regions, we generally all regard each other as American (although this is surely different for those from American territories such as Puerto Rico, Guam or American Samoa). Relocation may also be quite challenging for minorities, especially those moving to whiter states. But for the typical white American moving states, it is probably easier to relocate than for an Italian moving from Calabria or Napoli to Lombardia.
I've lived in 8 states and I think that some half-hearted jokes about dating cousins or eating possum are about the most trouble I've gotten by hailing from the Ozarks. In my experience there are also larger biases against neighboring states (sports rivals) than far-away states. Freud's narcissism of small difference and all that.
That being said, since at least the Reconstruction era following the Civil War, there has been some local to regional resistance to internal migration. Interestingly, today much of the resistance is put forth by residents of less economically developed regions against those from more well-off places moving in, pricing the locals out, and changing the culture. These changes are a sort of Californication, the gentrification of mountain towns by richer and more liberal whites, rather than poorer immigrants bringing down property values or taking manual labor jobs. While there is little by way of legislation against this, there is talk of some [3].
[1]: https://www.citylab.com/life/2019/03/mobile-stuck-us-geograp...
[2]: https://ec.europa.eu/eurostat/statistics-explained/index.php...
[3]: https://en.wikipedia.org/wiki/Immigration_to_the_United_Stat...
[4]: https://www.latimes.com/california/story/2019-11-10/go-back-...